UNIVERSITY OF NAIROBI
DEPARTMENT OF CIVIL AND CONSTRUCTION ENGINEERING
PERFOMANCE ANALYSIS OF NAIROBI EASTERN BYPASS
Nairobi Eastern Bypass Capacity and Level of Service Study
BY
MAMBO EDWIN KIMANI
Reg. No. F16/36416/2010
A project submitted as a partial fulfillment of the requirement for the
award of the degree of
BACHELOR OF SCIENCE IN CIVIL & CONSTRUCTION ENGINEERING
2015
PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
PERFOMANCE
ANALYSIS OF
NAIROBI EASTERN
BYPASS
A CAPACITY AND LEVEL OF SERVICE ANALYSIS OF NAIROBI EASTERN BYPASS
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
DEDICATION
I dedicate this project to:
 My parents, Mr. and Mrs. Benedict Mambo. Through their sacrifice and effort I was able
to get this far.
 Dr. Mary W. Kimani for the kindness of her heart and her sacrifice in seeing me through
school.
 Martin and Joyce Kimani for their prayer and support in my academic journey.
 My siblings, friends and classmates who have been with me throughout my academic
journey.
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
ACKNOWLEDGEMENTS
My greatest gratitude goes to the Almighty God for the strength and provision that enabled me to
complete this study.
I express my grateful appreciation to my supervisor, Eng. G.P.K Matheri, and Lecturer at The
University of Nairobi , Department of Civil and Construction Engineering, who played an
important role in guiding me and giving me invaluable advice on the study during its inception
and development.
I also wish to thank all my classmates who assisted me in the collection of data.
Thank you all.
Mambo Edwin Kimani
April 2015
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
ABSTRACT
The continued increase in the number of motor vehicles in Kenya has led to great congestion on
our roads, especially in the capital city Nairobi. The number of cars accessing Nairobi streets is
rising by the day and this has led to major traffic snarl ups, as well as an increased number of
accidents. These congestions are especially common on the highway comprising of Mombasa
road, Uhuru Highway and Waiyaki Way, which is the main highway going through the city of
Nairobi. Vehicles with no business in the Central Business District have for a long time been
forced to use Uhuru Highway for lack of an alternative route. The congestion led to Kenya
National Highways Authority designing and constructing alternate routes for such vehicles. Thus
the inception, construction and operation of the three main bypasses around Nairobi, which are
the Eastern, Northern, and Southern Bypasses.
The Nairobi Eastern Bypass project is a project that was started back in January 2011 and
completed in May 2012. This section of the bypass starts from Mombasa road at the Cabanas
interchange, passes through Pipeline and then Utawala and goes over Kangundo Road. The
Eastern Bypass then proceeds all the way to the recently constructed Thika Super Highway. The
total length of this section of road is 39km. The Nairobi Eastern bypass is an Asphalt Concrete
pavement and is classified as a class B road. The Nairobi Eastern bypass is a two lane, two way
single carriageway that is 9 m wide and has an open channel earth surface drain on either side.
The Eastern Bypass was constructed to help ease the traffic congestion along Mombasa Road,
through Uhuru Highway and into Waiyaki Way. For the purpose of this study, the stretch from
Thika Superhighway to the Kangundo Road junction will be considered.
The performance evaluation established the capacity of the road and traffic flow being handled
by the road in vehicles per hour. The study also determined the level of service of the road. In
order to achieve the above parameters, a field data collection and analysis was done. The
findings of the study have been properly outlined in chapter 4, 5 and 6 of this report. The
objectives, which were to determine the operational capacity and level of service of the Nairobi
Eastern Bypass, were met. In chapter 7 of this report, a number of recommendations have been
forwarded based on the findings. Should these recommendations be implemented, then the
problem of congestion on the road may be solved.
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
Table of Contents
1. INTRODUCTION .................................................................................................................................... 1
1.1 GENERALINTRODUCTION ............................................................................................................ 1
1.2 BACKGROUND TO ROAD TRANSPORTATION IN KENYA ..................................................... 1
1.3 STUDY AREA ................................................................................................................................... 1
1.4 PROBLEM STATEMENT ............................................................................................................... 3
1.5 OBJECTIVES AND SCOPE OF STUDY.......................................................................................... 4
1.6 METHOD OF STUDY ..................................................................................................................... 4
2. CHAPTER TWO: LITERATURE REVIEW ........................................................................................... 5
2.1. INTRODUCTION ............................................................................................................................. 5
2.1.1. TWO LANE HIGHWAYS ......................................................................................................... 5
2.2 DEFINITION OF TERMS.................................................................................................................. 6
2.2.1. Flow, Speed, Density Relationship. ............................................................................................ 7
2.2.2. LEVEL OF SERVICE (LOS) FOR AN URBAN SINGLE CARIAGEWAY HIGHWAY: ...... 8
2.3 FACTORS AFFECTING CAPACITY AND LOS........................................................................... 10
2.3.1. Base Conditions ....................................................................................................................... 10
2.3.2. Roadway Conditions ................................................................................................................ 10
2.3.3 Traffic Conditions ..................................................................................................................... 11
2.3.4 Control Conditions ..................................................................................................................... 11
2.3.5 Technology ............................................................................................................................... 11
2.4 ROAD CLASSIFICATION IN KENYA .......................................................................................... 11
2.4.1. Existing Road Classification System in an Urban Context ....................................................... 11
2.4.2. Review of Kenyan Road Classification System by Kenya Roads Board................................. 13
2.5 CLASSIFICATION OF TWO-LANE HIGHWAYS (HCM 2000).................................................. 14
2.6 LITERATTURE BACKGROUND ON STUDY AREA ................................................................. 15
2.8 THEORETICAL BACKGROUND. ................................................................................................. 16
2.8.1 Average Annual Daily Traffic (AADT) ..................................................................................... 16
2.8.2 Average Daily Traffic (ADT) .................................................................................................... 16
2.8.3 Peak Hour Volume (PHV) ........................................................................................................ 16
2.8.4 Vehicle Classification (VC) ...................................................................................................... 17
2.8.5 Vehicle Miles of Travel (VMT) ................................................................................................. 17
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
2.9 CAPACITY....................................................................................................................................... 17
2.10 TRAFFIC VOLUME COUNT ....................................................................................................... 17
3.1.1 Manual Count Method ............................................................................................................... 18
2.10 DETERMINATION OF LEVEL OF SERVICE FOR A TWO LANE TWO WAY HIGHWAY . 19
2.10.1 TWO WAY TWO LANE SEGMENTS .................................................................................. 20
2.10.2 Determining LOS ..................................................................................................................... 30
3. DATA COLLECTION .......................................................................................................................... 31
3.1 TRAFFIC VOLUME COUNT ......................................................................................................... 31
3.2 SPEED COUNT................................................................................................................................ 32
4. RESULTS AND ANALYSIS ................................................................................................................ 34
4.1 RESULTS ......................................................................................................................................... 34
4.1.1 TRAFFIC COUNT RESULTS .................................................................................................. 34
4.1.2 SPEED COUNT RESULTS ...................................................................................................... 43
4.2 ANALYSIS ....................................................................................................................................... 44
4.3 DETERMINING LEVEL OF SERVICE OF THE ROAD. ............................................................. 50
4.3.1 Determining free flow speed. .................................................................................................... 50
4.3.2 Determining Demand Flow Rate .............................................................................................. 52
4.3.3 Determining The Average Travel Speed.................................................................................... 53
4.3.4 Determining Percent Time Spent Following.............................................................................. 54
4.3.5 Determining Level Of Service .................................................................................................. 54
5. DISCUSSION ......................................................................................................................................... 56
5.1 DISCUSSION ON TRAFFIC FLOW RESULTS ............................................................................ 56
5.1.1 MORNING TRAFFIC ............................................................................................................... 56
5.1.2 EVENING TRAFFIC ................................................................................................................ 57
5.1.3 MID DAY TRAFFIC ................................................................................................................. 58
5.1.4 OFF PEAK TRAFFIC .............................................................................................................. 58
5.2 DISCUSSION ON SPEED-FLOW RESULTS ................................................................................ 59
6. CONCLUSION ....................................................................................................................................... 60
6.1 CAPACITY AND LEVEL OF SERVICE........................................................................................ 60
7. RECOMMENDATIONS ........................................................................................................................ 61
7.1 IMPROVING THE INFRASTRUCTURE ....................................................................................... 61
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
7.2 TRAFFIC MANAGEMENT ............................................................................................................ 62
8. LIST OF REFERENCES ........................................................................................................................ 63
9. APPENDICES ........................................................................................................................................ 63
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LIST OF TABLES
Table 2.1: Pcu for different types of vehicle………………………………………………….. 7
Table 2.2: Road classification in an urban context …………….............................................. 12
Table 2.3: Functional road classification …………………………………………………….. 12
Table 2.4: Summary of current road classification in km in Kenya …………………………. 13
Table 2.5: LOS criteria for two lane highways in class 1 …………………………………... 21
Table 2.6: Grade adjustment factor (fg) to determine speeds on two-way
and directional segments …………………………………………………..…….. 24
Table 2.7: Grade adjustment factor (fg) to determine percent time-spent-following
on two-way and directional segments ……………………………………….….. 24
Table 2.8: Passenger-car equivalents for trucks and RVs to determine speeds of
two-way and directional segments ………………………………………………. 25
Table 2.9: Passenger-car equivalents for trucks and RVs to determine percent
time-spent-following on two-way and directional segments ……………………… 25
Table 2.10: Adjustment (fnp) for effect of no-passing zones on average travel
speed on two-way segments ……………………………………………………
28
Table 2.11: Adjustment (fd/np) for combined effect of directional distribution
of traffic and percentage of no-passing zones on percent
time-spent-following on two-way segments …………………………………..
29
Table 4.1:
Traffic volume counts headed to Kangundo Road ……………………………
34
Table 4.2:
Traffic Volume Counts headed to Thika Road ………………………………
35
Table 4.3:
Corrected PCU Values for the traffic count headed to Kangundo Road …….. 37
Table 4.4:
Corrected PCU Values for the traffic count headed to Thika Road …………
38
Table 4.5:
Average 15 minute traffic headed to Kangundo Road ……………………….
39
Table 4.6:
Average 15 minute traffic headed to Thika Road ……………………………. 40
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
Table 4.7:
Average Hourly Traffic Headed to Kangundo Road …………………………
42
Table 4.8:
Hourly Traffic counts headed to Thika Road ………………………………..
42
Table 4.9:
Directional Split ……………………………………………………………… 43
Table 4.10:
Speed Counts for both directions …………………………………………………..… 43
Table 4.11:
Proportion of Trucks and RVs headed to Kangundo Road …………………… 51
Table 4.12:
Proportion of Trucks and RVs headed to Thika Road ………………………..
51
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
LIST OF FIGURES
Figure 1.1:
General view of Nairobi roads …………………………………………….… 2
Figure 1.2:
Aerial view of Study Area……………………………………………………
2
Figure 1.3:
Photo of Km 1+800 from the Thika Superhighway Junction ………………
3
Figure 2.1:
Figure showing level of service in relation to the operating
speeds and the volume/capacity ratio…………………………………..…
Figure 2.2:
Methodology for determining the capacity and LOS of a two
lane highway………………………………………………………………
Figure 2.3:
47
Graph Of Average Hourly Traffic Approaching from Thika
Road and Exiting to Kangundo Road …………………………………….
Figure 4.6:
46
Graph Of Average 15 Min Traffic Approaching from Kangundo
Road and Exiting to Thika Road ……………………………………….….
Figure 4.5:
45
Graph Of Average 15 Min Traffic Approaching from Thika Road
and Exiting to Kangundo Road …………………………………………
Figure 4.4:
44
Graph of Numbers of Different Types of Vehicles Headed
to Thika Road ……………………………………………………………
Figure 4.3:
21
Graph of Number of Different Types of Vehicles headed to
Kangundo Road …………………………………………….……………
Figure 4.2:
20
Graphical representation of los criteria for two lane highways in
class 1 ……………………………………………………………………..
Figure 4.1 :
8
48
Graph Of Average Hourly Traffic Approaching from Kangundo
Road and Exiting to Thika Road …………………………………………..
49
Figure 4.7:
Pie Chart Showing Directional Split Between The Two Directions ……….
50
Figure 4.8:
Figure Showing The level of service of the Road …………………………..
55
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
1. INTRODUCTION
1.1 GENERALINTRODUCTION
Transportation is concerned with the efficient and safe movement of people and goods from one
point to another. It is the core means in which any thriving community can achieve development.
It is therefore important for any civilization to integrate its transportation plans in its overall
economic plans and make development of transportation infrastructure part of its overall
development objectives. These objectives should be both in the long term as well as the short
term. In the long term, they are called Strategic Transportation Planning. These long term plans
involve a lot of complex procedures, rigorous studies as well as major financial requirements for
their budgets. On the other hand, short term plans are called Transportation System Management
(TSM)
As engineers are carrying out the initial design for the various transportation facilities in an area,
not only should they consider solving a particular problem at hand, but it is also important for
them to consider the current and future expected demand for the facilities they are designing.
However, the future demand for these designed facilities sometimes exceeds what the engineers
had projected. This leads to overcrowding of these facilities, leading to a strain not only to the
users, but to the facilities as well. This happens when there is a sudden growth in population
which leads to a higher number of goods.
1.2 BACKGROUND TO ROAD TRANSPORTATION IN KENYA
Road transport is the predominant mode of transport and carries about 93% of all cargo and
passenger traffic in Kenya.
The Kenya Roads Board has established Kenya's road network to be 160,886 km long. About
61,936km of these roads are classified according to the while the remaining 98,950km are not
classified.
Responsibility for the management of the road network falls under the Ministry of Transport and
Infrastructure and implemented through Kenya National Highways Authority (KeNHA), Kenya
Rural Roads Authority (KeRRA), Kenya Urban Roads Authority (KURA) and Kenya Wildlife
Service (KWS). The Eastern Bypass falls under the management of the Kenya National
Highways Authority. (KRB1)
1.3 STUDY AREA
The study area is the Nairobi Eastern By-Pass. The section of concern is from Thika
Superhighway to the junction of Kangundo Road. The section has a total distance of 13.75
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
kilometers. The Eastern Bypass is an urban highway situated on the Eastern side of the Capital
City of Kenya; Nairobi.
Figure 1.1: General view of Nairobi roads
Figure 1.2: Aerial view of Study Area.
Source: Google Earth
Source: Google Maps
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
Figure 1.3: Map of Km 1+800 from the Thika Superhighway Junction
Source: Google Maps
As is clear from the map, the section from Thika Road is heavily built and densely populated,
hence the increased traffic on the road.
The Eastern Bypass is an Asphalt Concrete pavement and is classified as a class B road. The
Bypass is a two lane, two way single carriageway that is 9 m wide and has an open channel earth
surface drain on either side. The Bypass has a road reserve of 30m and has average access
control. Most people living along the Bypass can access it directly from almost all its length. The
abutting land along the Eastern Bypass is mainly used for agroforestry on the Western side and
businesses on the Eastern side.
1.4 PROBLEM STATEMENT
The Nairobi Eastern Bypass is currently faced with the problem of vehicular traffic congestion
which has led to long traffic queues. This has been contributed to by a number of factors which
comprise all vehicle classes. Such factors include the slow moving lorries and fourteen seater
public service vehicles (matatus) using the Bypass. Four seater personal vehicles and Sports
Utility Vehicles have also increased in numbers on the roads. These long queues and shockwaves
have led to a great reduction in the performance of the Eastern Bypass. This study will determine
if the capacity has overshot 3400 pc/h (design capacity for a two lane two way highway in both
directions)
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
1.5 OBJECTIVES AND SCOPE OF STUDY
This study aims at determining the operational capacity of Eastern Bypass, as well as
determining its operational level of service.
To achieve the above objectives, the scope of this study will entail: field traffic data collection,
traffic volume analysis and level of service analysis.
1.6 METHOD OF STUDY
The Highway Capacity Manual outlines appropriate procedures for the determination of the
traffic capacity of a road. The process involves carrying out a field traffic count. This collected
data is then analyzed by a procedure laid out on the Highway Capacity Manual. It is then used to
determine the capacity.
The Highway Capacity Manual outlines that a speed count should be carried out and this used
with the operational capacity to determine the Level of Service.
In light of this, field data collection on capacity and speed was carried out. This entailed
conducting traffic counts as well as a speed survey. A literature review on the subject of capacity
was also done. A review of previous studies on the road was also done. After all the studies were
finished, an analysis of the collected data was also carried out.
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
2. CHAPTER TWO: LITERATURE REVIEW
2.1. INTRODUCTION
2.1.1. TWO LANE HIGHWAYS
Two-lane highways are a key element in the highway systems of most countries. They perform a
variety of functions, are located in all geographic areas, and serve a wide range of traffic. Any
consideration of operating quality must account for these disparate functions.(HCM2010)
Traffic operations on two-lane, two-way highways differ from those on other uninterrupted-flow
facilities. Lane changing and passing are possible only in the face of oncoming traffic in the
opposing lane. Passing demand increases rapidly as traffic volumes increase, and passing
capacity in the opposing lane declines as volumes increase.(HCM2010)
Therefore, on two-lane highways, unlike other types of uninterrupted-flow facilities, normal
traffic flow in one direction influences flow in the other direction. Motorists must adjust their
travel speeds as volume increases and the ability to pass declines.(HCM2010)
Efficient mobility is the principal function of major two-lane highways that connect major traffic
generators or that serve as primary links in state and national highway networks. These routes
tend to serve long-distance commercial and recreational travelers, and long sections may pass
through rural areas without traffic-control interruptions. Consistent high-speed operations and
infrequent passing delays are desirable for these facilities.(HCM2010)
Other paved, two-lane rural highways serve for accessibility. They provide all-weather access to
an area, often for relatively low traffic volumes. Cost-effective access is the dominant
consideration. Although beneficial, high speed is not the principal concern. Delay—as indicated
by the formation of platoons—is more relevant as a measure of service quality.(HCM2010)
Two-lane roads also serve scenic and recreational areas in which the vista and environment are
meant to be experienced and enjoyed without traffic interruption or delay. A safe roadway is
desired, but high-speed operation is neither expected nor desired. For these reasons, there are two
performance measures to describe service quality for two-lane highways: percent time-spentfollowing and average travel speed.(HCM2010)
Percent time-spent-following represents the freedom to maneuver and the comfort and
convenience of travel. It is the average percentage of travel time that vehicles must travel in
platoons behind slower vehicles due to the inability to pass. Percent-time-spent-following is
difficult to measure in the field. However, the percentage of vehicles traveling with headways of
less than 3sec at a representative location can be used as a surrogate measure. (HCM2000)
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
Average travel speed reflects the mobility on a two-lane highway: it is the length of the highway
segment divided by the average travel time of all vehicles traversing the segment in both
directions during a designated interval.(HCM2010)
LOS criteria use both these performance measures. On major two-lane highways, for which
efficient mobility is paramount, both percent time-spent-following and average travel speed
define LOS. However, roadway alignments with reduced design speeds will limit the LOS that
can be achieved. On highways for which accessibility is paramount and mobility less critical,
LOS is defined only in terms of percent time-spent-following, without consideration of average
travel speed.(HCM2010)
2.2 DEFINITION OF TERMS
Flow (Q): This is the number of vehicles accessing a given part of the road per unit time. This is
mainly measured in vehicles per hour. Traffic flow can be divided into two main types:
interrupted flow and uninterrupted flow. Uninterrupted flow occurs when vehicles traversing a
length of roadway are not required to stop by any cause external to the traffic stream, such as
traffic control devices. It is most common in highways or interstates where there is limited
access. Interrupted flow occurs when flow is periodically interrupted by external means mainly
traffic signs and signals. It is common in urban centers and roads with unlimited access control.
(Myer Kutz,2004)
Density (K): This refers to the number of vehicles on a given length of roadway or lane. It is
determined in terms of vehicles per mile or per kilometer. It is a very difficult parameter to
obtain and is mainly done by aerial photography. This makes it very expensive to obtain.
Speed (V): Myer Kutz(2004) defines speed as the distance a vehicle travels per unit time. It is the
inverse of the time taken by a vehicle to traverse a given distance. In a highway, most vehicles
will be traveling at different speeds. In quantifying traffic stream, the average speed is important.
The average speed is found by averaging the individual speeds of all the vehicles in the study
area.Speed is determined from the distance covered by a vehicle in unit time, or for a number of
observations, the mean is computed from the distribution of speeds and is known as the time
mean speed and if from the mean of the space distribution of speeds, it is known as the space
mean speed. (Ashford and Wright, 2007)
Kadiyali,1997 outlines the three principal classifications of speed as follows:
i.
ii.
iii.
Spot Speed: Is the instantaneous speed of a vehicle at a specified point along a
road.
Journey speed: Is the effective speed of a vehicle on a trip between two points.
Running speed: Is the average speed over a trip when the vehicle is moving.
According to Kadiyali,1997, there are three basic approaches that may be used to collect speed
data. These are:
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
Measuring the travel time of a vehicle between two detectors or observers separated by a
known fixed distance.
Measuring time taken by a vehicle to cross an induction loop set at a road section.
Measuring speed directly on the basis of the Doppler principle, i.e. using a radar speed
meter, better known as a speed gun.
2.2.1. Flow, Speed, Density Relationship.
These three parameters are the fundamentals for measuring the operation performance and level
of service of a transportation facility such as a highway. Under uninterrupted conditions, flow,
density and speed are related by the following equation
Flow = Density × Speed
Q = K × V
Equation 1.
Capacity: According to Myer Kutz(2004), capacity is defined as a measure of the demand that a
highway can potentially service. The Highway Capacity Manual (2010) defines capacity as “the
maximum hourly rate at which persons or vehicles can be reasonably expected to traverse a point
or uniform segment of a lane or roadway during a given time period, under prevailing roadway,
traffic and roadway conditions”.(HCM 2010)
Demand: This is the principle measure of the amount of traffic using a given facility (HCM
2010)
Passenger Car Units (PCU): A traffic stream normally consists of different kinds of vehicles. To
allow for capacity measurements for roads, traffic volumes are normally expressed in Passenger
Car Units(PCU). As different kinds of vehicles affect the capacity of rural roads, urban roads and
junctions in varying degrees, the weight of each class of vehicle has to be varied to suit the
purpose for which it is to be used (Kadiyali, 1997). Table 2.1 shows the main conversion factors
for various vehicle types that have been used for this study.
Table 2.1: PCU FOR DIFFERENT TYPES OF VEHICLES.
Vehicle Type
PCU
Motorcycles
0.33
Cars
1
Vans and Minibuses
2
Buses
2.5
Trucks
Source: Ministry of Transport and Communication, 2007
3
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
2.2.2. LEVEL OF SERVICE (LOS) FOR AN URBAN SINGLE CARIAGEWAY HIGHWAY:
Myer Kutz(2004) defines the level of service as a qualitative measure of a highway’s operating
conditions under a given demand within a traffic stream and their perception by motorists and/or
passengers. It relates the quality of traffic service to given volumes of traffic. There are six levels
of service ranging from A to F (HCM 2010). They are outlined below as in the HCM (2010)
Figure 2.1: Figure showing level of service in relation to the operating speeds and the
volume/capacity ratio.
Level of Service A: This describes the highest quality of traffic service, when motorists are able to
travel at their desired speed. Without strict enforcement, this high quality would result in average
speeds of 90 km/h or more in two way urban and rural highways in Class I. The passing
frequency required to maintain these speeds has not reached a demanding level, so that passing
demand is well below passing capacity, and platoons of three or more vehicles are rare. Drivers
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
are delayed no more than 35% of their travel time by slow moving vehicles. A maximum flow
rate of 490 pc/h total in both directions may be achieved with base conditions. On Class II
highways, speeds may fall below 90 km/h but motorists will not be delayed more than 40% of
their travel time in platoons.
Level of Service B: This characterizes traffic flow with speeds of 80 km/h or slightly higher on
level terrain Class I highways. The desire for passing to maintain desired speeds becomes
significant and approximates the passing capacity at the lower boundary of the Los B. Drivers
are delayed in platoons up to 50% of the time. Service flow rates of 780 pc/h total in both
directions can be achieved under base conditions. Above this flow rate, the number of platoons
increases dramatically. On Class II highways, speeds may fall below 80 km/h, but motorists will
not be delayed in platoons for more than 55% of their travel time.
Level of Service C: Describes further increases in flow, resulting in noticeable increases in platoon
formation, platoon size and frequency of passing impediments. The average speed still exceeds
70 km/h on level terrain Class I highways, even though unrestricted passing demand exceeds
passing capacity. At higher volumes, the chaining of platoons and significant reductions in
passing capacity occur. Although traffic flow is stable, it is susceptible to congestion due to
turning traffic and slow moving vehicles. Percent time spent following may reach 65%. A
service flow rate of up to 1190 pc/h total in both directions can be accommodated under base
conditions. On Class II highways, speeds may fall below 70 km/h, but motorists will not be
delayed in platoons for more than 70% of their travel time.
Level of Service D: Describes unstable traffic flow. The two opposing traffic streams begin to
operate separately at higher volume levels, as passing becomes extremely difficult. Passing
demand is high, but passing capacity approaches zero. Mean platoon sizes of 5 to 10 vehicles are
common, although speeds of 60 km/h still can be maintained under base conditions on Class I
highways. The proportion of no passing zones along the roadway section usually has little
influence on passing. Turning vehicles and roadside distractions cause major shock waves in the
traffic stream. Motorists are delayed in platoons for nearly 80% of their travel time. Maximum
service flow rates of 1830 pc/h total in both directions can be maintained under base conditions.
On Class II highways, speeds may fall below 60 km/h but in no case will motorists be delayed in
platoons for more than 85% of their travel time.
Level of Service E: Traffic flow conditions have a percent time-spent-following greater than 80%
on Class I highways and greater than 85% on Class II. Even under base conditions, speeds may
drop below 60 km/h. Average travel speeds on highways with less than base conditions will
slower, even down to 40 km/h on sustained upgrades. Passing is virtually impossible at LOS E,
and platooning becomes intense, as slower vehicles or other interruptions are encountered. The
highest volume attainable under LOS E defines the capacity of the highway, generally 3,200 pc/h
total in both directions. Operating conditions at capacity are unstable and difficult to predict.
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
Traffic operations seldom reach near capacity on rural highways, primarily because of lack of
demand.
Level of Service F: Represents heavily congested flow with traffic demand exceeding capacity.
Volumes are lower than capacity and speeds are highly variable.
2.3 FACTORS AFFECTING CAPACITY AND LOS
The Highway Capacity Manual (HCM2010) outlines the following as the factors that affect the
capacity and Level of service of a two way two lane single carriageway.
2.3.1. Base Conditions
Base conditions assume good weather, good pavement conditions, users familiar with the
facility, and no impediments to traffic flow. Base conditions for uninterrupted-flow facilities
include the following
 Lane widths of 3.6m,
 Clearance of 1.8m between the edge of the travel lanes and the nearest obstructions or
objects at the roadside and in the median,
 Free-flow speed of 100km/h for multilane highways,
 Only passenger cars in the traffic stream (no heavy vehicles),
 Level terrain,
 No no-passing zones on two-lane highways, and
 No impediments to through traffic due to traffic control or turning vehicles.
2.3.2. Roadway Conditions
Roadway conditions include geometric and other elements. In some cases, these influence the
capacity of a road; in others, they can affect a performance measure such as speed, but not the
capacity or maximum flow rate of the facility. Roadway factors include the following:







Number of lanes,
The type of facility and its development environment,
Lane widths,
Shoulder widths and lateral clearances,
Design speed,
Horizontal and vertical alignments, and
Availability of exclusive turn lanes at intersections
The horizontal and vertical alignment of a highway depends on the design speed and the
topography of the land on which it is constructed. In general, the severity of the terrain reduces
capacity and service flow rates. This is significant for two-lane rural highways, such as the case
study in this report where the severity of terrain not only can affect the operating capabilities of
individual vehicles in the traffic stream, but also can restrict opportunities for passing slowmoving vehicles.
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
2.3.3 Traffic Conditions
Traffic conditions that influence capacities and service levels include:
Vehicle Type: The entry of heavy vehicles into the traffic stream affects the number of vehicles
that can be served. Heavy vehicles adversely affect traffic in two ways:
 They are larger than passenger cars and occupy more roadway space; and
 They have poorer operating capabilities than passenger cars, particularly with respect to
acceleration, deceleration, and the ability to maintain speed on upgrades.
Directional and Lane Distribution: Directional distribution has a dramatic impact on two-lane
rural highway operation, which achieves optimal conditions when the amount of traffic is about
the same in each direction.
2.3.4 Control Conditions
For interrupted-flow facilities, the control of the time for movement of specific traffic flows is
critical to capacity, service flow rates, and level of service. The most critical type of control is
the traffic signal. The type of control in use, signal phasing, allocation of green time, cycle
length, and the relationship with adjacent control measures affect operations.
2.3.5 Technology
Emerging transportation technologies, also known as intelligent transportation systems (ITS),
will enhance the safety and efficiency of vehicles and roadway systems. ITS includes any
technology that allows drivers and traffic control system operators to gather and use real-time
information to improve vehicle navigation, roadway system control, or both.
2.4 ROAD CLASSIFICATION IN KENYA
2.4.1. Existing Road Classification System in an Urban Context
The complete functional classification system has been developed around the hierarchy of
movements: main movement, transition, distribution, collection, access and termination. It is
shown in Table 2.2. The two main shortcomings of the functional classification system in an
urban environment are that it does not consider other modes of transportation and does not
consider roadway functions outside of access and mobility. With respect to the lack of
consideration of other road users, it is arguable that the hierarchy of movements on which the
functional classification system is based is equally applicable to walking, cycling, public transit
and the private motor vehicle. However, the facilities that would serve “main movement” for a
motor vehicle are significantly different than the facilities serving the “main movement” for
pedestrians. Generally speaking, the movement of motor vehicle traffic requires a smooth, direct
and uninterrupted route and little in the way of amenities. In fact, clear zones at the side of the
road are preferable for safety and convenience. The movement of pedestrian traffic is influenced
much more by “comfort.”
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
Table 2.2: ROAD CLASSIFICATION IN AN URBAN CONTEXT
Classification Characteristics
Principal
Serves major centers of activity with the highest traffic volumes and longest trip
Arterial
lengths. Integrated internally and between major rural connections. Service to
abutting lands is subordinate to travel service to major movements. Design
types are interstate, other freeways and other principal arterials
Minor
Trips of moderate length at a lower level of mobility than principal arterials.
arterial
Some emphasis on land access. May carry local bus routes and provide
intracommunity continuity but does not penetrate neighborhoods.
Collector
Provides both land access and traffic circulation within all areas. Penetrates
neighborhoods and communities collecting and distributing traffic between
neighborhoods and the arterial streets.
Local
Primarily permits direct land access and connections to the higher order streets.
Lowest level of mobility. Through traffic is usually deliberately discouraged.
Source: Forbes G.
According to Kenya Roads Board, The Current Road Classification System in Kenya was
developed over 30 years ago and has six road classes named from Classes A to E and a Special
Purpose Road class. Each class is defined by the functional criteria related to administrative level
of centers the roads connect.
Table 2.3: FUNCTIONAL ROAD CLASSIFICATION IN KENYA
CLASS
DESCRIPTION
FUNCTION
A
International Trunk
Roads (Principal
Arterials)
Link centers of international importance and cross
international boundaries or terminate at international
ports or airports (e.g. Mombasa,)
B
National Trunk Roads
(Principal Arterials)
Link nationally important centers (e.g. Provincial
headquarters)
C
Primary Roads (Minor
Arterials)
Link provincially important centers to each other or
to higher class roads (e.g. District headquarters)
D
Secondary Roads (Minor Link locally important centers to each other, or to
Arterials)
more important centers or to a higher class road (e.g.
divisional headquarters)
E
Minor Roads (Collectors) Any link to a minor center
SPR
G (Locals)
Government Roads
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
U
L (Locals)
Settlement Roads
R (Locals)
Rural Access Roads
S (Locals)
Sugar Roads
T (Locals)
Tea Roads
W (Locals)
Wheat Roads
Unclassified
All other public roads and streets
Source: Kenya Roads Board
Table 2.4: SUMMARY OF CURRENT ROAD CLASSIFICATION IN KILOMETERS IN
KENYA
ROAD CLASS
PAVED
UNPAVED
TOTAL
A
2,772
816
3,588
B
1,489
1,156
2,645
C
2,693
5,164
7,857
D
1,238
9,483
10,721
E
577
26,071
26,649
SPR
100
10,376
10,476
U
2,318
96,623
98,941
TOTAL
11,189
149,689
160,886
Source: KRB.
2.4.2. Review of Kenyan Road Classification System by Kenya Roads Board
The current road classification system was developed over 30 years ago. Since then the road
network has grown rapidly and changed in character. The classification system is now perceived
to be outdated and in need of a review for a number of reasons. First, the rapid growth and
urbanization of the population has led to the requirement to update it. There has also been a
significant expansion of the road network. It is also important to provide additional road classes
to cater for special purpose roads. Another main reason is the existence of the large rural and
urban road network (98,936km) that is currently unclassified. The successive changes in
administration boundaries, affecting the validity of the original functional classification in terms
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
of administrative centers, notably at district level is also a reason for the revision of this
classification. The current classification has some anomalies in class assignment, whereby some
higher classes of roads have significantly lower standards or lower traffic volume than some
lower classes of roads. The criteria used for the classification are relatively broad and subjective.
The present system is seen to be static and unable to adjust to changing circumstances. Rational
planning and allocation of scarce funds to the road system is now perceived to require a more
objective and quantifiable basis for prioritizing groups of roads than a simple functional
classification system can provide.
Due to the limitations of the existing classification system, KRB, with funding from the Nordic
Development Fund under the Northern Corridor Transport Improvement Project, commissioned
a Consultant to develop a new Road Classification System in October 2006.The Consultant has
reviewed the current classification system and compared with best international practices to
develop a proposed new classification system.
The proposed reclassification system was presented to a stakeholder's meeting in July 2007
where it was adopted. It will take effect when approved by the Minister for Transport and
Infrastructure.
The Proposed Kenyan Road Classification System (Kenya Roads Board)
KRB proposed the new classification system. It covers all public roads and extends to the
presently unclassified rural and urban roads. The main thrust of the approach is to make the
classification more objective and consistent by specifying quantifiable parameters (traffic,
population, spacing) to guide the selection of appropriate road classes. It is also a dynamic
system where road classes can be periodically reviewed to adapt to changes in traffic, function
etc.
The proposed Road Classification System sees Kenya's road network as being composed of two
distinct networks i.e. the Rural Roads Network (outside Cities and Municipalities) and the Urban
Roads Network (within Cities and Municipalities) for all public roads with 9m or more road
reserves. Although the new classification system retains A,B,C,D and E classes, the system has
been extended to include additional classes. It should be noted that presently classified roads do
not necessarily retain their road classes under the new classification.
2.5 CLASSIFICATION OF TWO-LANE HIGHWAYS (HCM 2000)
Two-lane highways are categorized into two classes for analysis: (HCM 2010)
• Class I—These are two-lane highways on which motorists expect to travel at relatively high
speeds. Two-lane highways that are major intercity routes, primary arterials connecting major
traffic generators, daily commuter routes, or primary links in state or national highway networks
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
generally are assigned to Class I. Class I facilities most often serve long-distance trips or provide
connecting links between facilities that serve long-distance trips.
• Class II—These are two-lane highways on which motorists do not necessarily expect to travel
at high speeds. Two-lane highways that function as access routes to Class I facilities, serve as
scenic or recreational routes that are not primary arterials, or pass through rugged terrain
generally are assigned to Class II. Class II facilities most often serve relatively short trips, the
beginning and ending portions of longer trips, or trips for which sightseeing plays a significant
role.
The Eastern Bypass can be classified as a Class I highway since it provides a connecting link
between two roads that serve long-distance trips, that is Thika Superhighway and Mombasa
Road.
2.6 LITERATTURE BACKGROUND ON STUDY AREA
The area around the study area was originally an expansive bare land with no developments
around it. However with the coming of the road, a lot of development has taken place. Local
newspapers have depicted a spurt in the economic conditions of the area. According to the
Standard newspaper:
“the area opened up and everyone wants to live there due to accessibility to Nairobi. At the point
where the bypass connects to Kiambu-Ruiru Road before connecting to Thika Superhighway,
unprecedented growth has been experienced, with investors building palatial homes and
entertainment spots.” (Standard Media)
The paper further reports that business is booming in the area. The construction industry has thoroughly
grown in the time since the building of the road. This has led to the interruption of traffic flow by
construction vehicles and lorries.
Hardware shops are also reaping from the increased demand. Joseph Kiminda, a quarry business
owner, says: “There is no single day you will not find a construction project in progress. This
means good business for construction materials suppliers. We are busy.” (Standard Media)
The new road also introduced a route by the local transportation industry from the junction at
Thika road to the junction at Kangundo road. The route is operated by fourteen or eleven seater
vans known as matatus. These vehicles drop and pick passengers at random non-designated
points on the road. As the vehicles decelerate to stop, this creates a shockwave of the vehicles
behind it and increases the percentage time spent following. This imparts on the level of service
of the road. The vehicles also cause a shockwave behind them as they join the road. The
acceleration of these matatus cannot be compared with that of small personal cars and this causes
vehicles to slow down to allow for the matatus joining the traffic stream.
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
Since the main purpose of the road was to divert traffic that had no business in the Central
Business District, most of the goods trucks now use the Eastern Bypass. These trucks have a
speed limit of 65 km/h. This speed creates hindrance to the movement of light vehicles whose
speed limit is 110 km/h. This increases the percentage time spent following.
2.8 THEORETICAL BACKGROUND.
Traffic volume studies are conducted to collect data on the number of vehicles and/or pedestrians
that pass a point on a highway facility during a specified time period. Traffic volume studies are
usually conducted when certain volume characteristics are needed, some of which follow:
2.8.1 Average Annual Daily Traffic (AADT) is the average of 24-hour counts collected every day
of the year. AADTs are used in several traffic and transportation analyses for:
a. Estimation of highway user revenues
b. Computation of crash rates in terms of number of crashes per 100 million vehicle kilometers
c. Establishment of traffic volume trends
d. Evaluation of the economic feasibility of highway projects
e. Development of freeway and major arterial street systems
f. Development of improvement and maintenance programs
2.8.2 Average Daily Traffic (ADT) is the average of 24-hour counts collected over a number of
days greater than one but less than a year. ADTs may be used for:
a. Planning of highway activities
b. Measurement of current demand
c. Evaluation of existing traffic flow
2.8.3 Peak Hour Volume (PHV) is the maximum number of vehicles that pass a point on a
highway during a period of 60 consecutive minutes. PHVs are used for:
a. Functional classification of highways
b. Design of the geometric characteristics of a highway, for example, number of lanes,
intersection signalization, or channelization
c. Capacity analysis
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
d. Development of programs related to traffic operations, for example, one-way street systems or
traffic routing
e. Development of parking regulations
2.8.4 Vehicle Classification (VC) records volume with respect to the type of vehicles, for
example, passenger cars, two-axle trucks, or three-axle trucks. VC is used in:
a. Design of geometric characteristics, with particular reference to turning-radii requirements,
maximum grades, lane widths, and so forth
b. Capacity analyses, with respect to passenger-car equivalents of trucks
c. Adjustment of traffic counts obtained by machines
d. Structural design of highway pavements, bridges, and so forth
2.8.5 Vehicle Miles of Travel (VMT) is a measure of travel along a section of road. It is the
product of the traffic volume (that is, average weekday volume or ADT) and the length of
roadway in miles to which the volume is applicable. VMTs are used mainly as a base for
allocating resources for maintenance and improvement of highways.
2.9 CAPACITY
The capacity of a two-lane highway is 1,700 pc/h for each direction of travel. The capacity is
nearly independent of the directional distribution of traffic on the facility, except that for
extended lengths of two-lane highway, the capacity will not exceed 3,200 pc/h for both
directions of travel combined. For short lengths of two-lane highway—such as tunnels or
bridges—a capacity of 3,200 to 3,400 pc/h for both directions of travel combined may be
attained but cannot be expected for an extended length.
2.10 TRAFFIC VOLUME COUNT
Traffic volume studies are conducted to determine the number, movements, and classifications of
roadway vehicles at a given location. These data can help identify critical flow time periods,
determine the influence of large vehicles or pedestrians on vehicular traffic flow, or document
traffic volume trends. The length of the sampling period depends on the type of count being
taken and the intended use of the data recorded.
Two methods are available for conducting traffic volume counts:


manual
automatic
Manual counts are typically used to gather data for determination of vehicle classification,
turning movements, direction of travel, pedestrian movements, or vehicle occupancy. Automatic
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
counts are typically used to gather data for determination of vehicle hourly patterns, daily or
seasonal variations and growth trends, or annual traffic estimates.
The selection of study method should be determined using the count period. The count period
should be representative of the time of day, day of month, and month of year for the study area.
For example, counts at a summer resort would not be taken in January. The count period should
avoid special event such as weekends and public holidays or compromising weather conditions
such as heavy rain or snow conditions. Count periods may range from 5 minutes to 1 year.
Typical count periods are 15 minutes or 2 hours for peak periods, 4 hours for morning and
afternoon peaks, 6 hours for morning, midday, and afternoon peaks, and 12 hours for daytime
periods. For example, if you were conducting a 2 -hour peak period count, eight 15-minute
counts would be required. For this study, the Manual Count Method will be adopted.
2.10.1 Manual Count Method
This is the more common method of conducting traffic counts. It is mostly used where one
requires small samples of data at any given location. Manual counts are sometimes used when
the effort and expense of automated equipment are not justified. Manual counts are necessary
when automatic equipment is not available. Manual counts are typically used for periods of less
than a day. Normal intervals for a manual count are 5, 10, or 15 minutes. Traffic counts during a
Monday morning rush hour and a Friday evening rush hour may show exceptionally high
volumes and are not normally used in analysis; therefore, counts are usually conducted on a
Tuesday, Wednesday, or Thursday.
2.10.1.1 Manual Count Recording Methods
Manual counts are recorded using one of three methods: tally sheets, mechanical counting
boards, or electronic counting boards. For this study, only data sheets and counting boards will
be used.
2.10.1.1.1 Tally Sheets
Recording data onto tally sheets is the simplest means of conducting manual counts. The data
can be recorded with a tick mark on a pre-prepared field form. A watch or stopwatch is necessary
to measure the desired count interval.
2.10.1.1.2 Mechanical Counting Boards
Mechanical count boards consist of counters mounted on a board that record each direction of
travel. Common counts include pedestrian, bicycle, vehicle classification, and traffic volume
counts. Typical counters are push button devices with three to five registers. Each button
represents a different stratification of type of vehicle or pedestrian being counted. The limited
number of buttons on the counter can restrict the number of classifications that can be counted on
a given board. A watch or a stopwatch is also necessary with this method to measure the desired
count interval.
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
2.10.1.2 Personnel Involved in a Manual Count Study
The size of the data collection team depends on the length of the counting period, the type of
count being performed, the number of lanes or crosswalks being observed, and the volume level
of traffic. The number of personnel needed also depends on the study data needed. For example,
one observer can record certain types of vehicles while another counts total volumes. Observers
conducting manual traffic counts must be trained on the study purpose. To avoid fatigue,
observers must be relieved periodically. Every 2 hours observers should take a 10 to 15 minute
break.
2.10.1.3 Key Steps to a Manual Count Study
A manual count study includes three key steps:
Perform necessary office preparations.
Select proper observer location.
Label data sheets and record observations.
Perform Necessary Office Preparations
Office preparations start with a review of the purpose of the manual count. This type of
information will help determine the type of equipment to use, the field procedures to follow, and
the number of observers required. For example, an intersection with multiple approach lanes may
require electronic counting boards and multiple observers.
Select Proper Observer Location
Observers must be positioned where they have a clear view of the traffic. Observers should be
positioned away from the edge of the roadway. If observers are positioned above ground level
and clear of obstructions they usually have the best vantage point. Visual contact must be
maintained if there are multiple observers at a site. If views are unobstructed, observers may
count from inside a vehicle.
Label Data Forms and Record Observations
Manual counts may produce a large number of data forms; therefore, the data forms should be
carefully labeled and organized. On each tally sheet, the observer should record the location,
time and date of observation, and weather conditions24.
2.11 DETERMINATION OF LEVEL OF SERVICE FOR A TWO LANE TWO
WAY HIGHWAY
HCM 2000 outlines the following discussion presenting estimates of two-lane highway capacity,
defining the LOS for two-lane highways, and documenting the methodology for operational and
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
for planning applications. Figure 7 summarizes the methodology for determining the Capacity
and the Level of service of a Two Lane highway.
Figure 2.2: Methodology for determining the capacity and LOS of a two lane highway.
Source: Highway Capacity Manual 2010
2.11.1 TWO WAY TWO LANE SEGMENTS
The two-way segment methodology estimates measures of traffic operation along a section of
highway, based on terrain, geometric design, and traffic conditions. Terrain is classified as level
or rolling, as described below. Mountainous terrain is addressed in the operational analysis of
specific upgrades and downgrades, presented below. This methodology typically is applied to
highway sections of at least 2.0 mi. Traffic data needed to apply the two-way segment
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
methodology include the two-way hourly volume, a peak-hour factor (PHF), and the directional
distribution of traffic flow. The PHF may be computed from field data, or appropriate default
values may be selected from the tabulated values presented in Chapter 12 of HCM2000. Traffic
data also includes the proportion of trucks and recreational vehicles (RVs) in the traffic stream.
The operational analysis of extended two-way segments for a two-lane highway involves several
steps, described in the following sections.
Table 2.5: LOS CRITERIA FOR TWO LANE HIGHWAYS IN CLASS 1 (HCM2000)
Source: Highway Capacity Manual 2010
Figure 2.3: GRAPHICAL REPRESENTATION OF LOS CRITERIA FOR TWO LANE
HIGHWAYS IN CLASS 1
Source: Highway Capacity Manual 2010
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
2.11.1.1 Determining Free-Flow Speed (HCM2000)
A key step in the assessment of the LOS of a two-lane highway is to determine the free-flow
speed (FFS). The FFS is measured using the mean speed of traffic under low flow conditions (up
to two-way flows of 200 pc/h). If field measurements must be made with two-way flow rates of
more than 200 pc/h, a volume adjustment must be made in determining FFS. This volume
adjustment is discussed below.
The FFS of a highway can be determined directly from a speed study conducted in the field. No
adjustments are made to the field-measured data. The speed study should be conducted at a
representative location within the highway segment being evaluated; for example, a site on a
short upgrade should not be selected within a segment that is generally level. Any speed
measurement technique acceptable for other types of traffic engineering speed studies may be
used. The field study should be conducted in periods of low traffic flow (up to a two-way flow of
200 pc/h) and should measure the speeds of all vehicles or of a systematic sampling (e.g., of
every 10th vehicle). A representative sample of the speeds of at least 100 vehicles, impeded or
unimpeded, should be obtained.
If the speed study must be conducted at a two-way flow rate of more than 200 pc/h, the FFS can
be found by using the speed-flow relationships shown in Chapter 12(HCM2000), assuming that
data on traffic volumes are recorded at the same time. The FFS can be computed based on field
data as shown in Equation 2:
(Equation 2)
Source: Highway Capacity Manual 2010
where
FFS = estimated free-flow speed (km/h),
SFM = mean speed of traffic measured in the field (km/h),
Vf = observed flow rate for the period when field data were obtained (veh/h), and
fHV = heavy-vehicle adjustment factor, determined as shown in Equation 5
2.11.1.2 Determining Demand Flow Rate
Three adjustments must be made to hourly demand volumes, whether based on traffic counts or
estimates, to arrive at the equivalent passenger-car flow rate used in LOS analysis. These
adjustments are the PHF, the grade adjustment factor, and the heavy vehicle adjustment factor.
These adjustments are applied according to Equation 3.
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
(Equation 3)
Source: Highway Capacity Manual 2010
where
vp = passenger-car equivalent flow rate for peak 15-min period (pc/h),
V = demand volume for the full peak hour (veh/h),
PHF = peak-hour factor,
fG = grade adjustment factor, and
fHV = heavy-vehicle adjustment factor determined as shown in Equation 5
2.11.1.3 PHF
PHF represents the variation in traffic flow within an hour. Two-lane highway analysis is based
on demand volumes for a peak 15-min period within the hour of interest—usually the peak hour.
For operational analysis, the full-hour demand volumes must be converted to flow rates for the
peak 15 min, as shown in Equation 3. The peak hour factor is then calculated using Equation 4.
𝑃𝐻𝐹 =
𝑉
𝑉15 𝑋 4
(Equation 4)
Source: Highway Capacity Manual 2010
Where:
PHF = Peak Hour Factor
V = Hourly volume (veh/h)
V15 = Maximum 15 minute rate of flow
Default PHF values of 0.88 for rural areas and 0.92 for urban areas may be used in the absence
of local data.
2.11.1.4 Grade Adjustment Factor
The grade adjustment factor, fG, accounts for the effect of the terrain on travel speeds and percent
time-spent-following, even if no heavy vehicles are present. The values of the grade adjustment
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
factor are listed in Table 5 for estimating average travel speeds and in Table 6 for estimating
percent time-spent-following.
Table 2.6: GRADE ADJUSTMENT FACTOR (fG) TO DETERMINE SPEEDS ON TWOWAY
AND DIRECTIONAL SEGMENTS
Source: Highway Capacity Manual 2010
Table 2.7: GRADE ADJUSTMENT FACTOR (fG) TO DETERMINE PERCENT TIMESPENT-FOLLOWING ON TWO-WAY AND DIRECTIONAL SEGMENTS
Source: Highway Capacity Manual 2010
2.11.1.5 Adjustment for Heavy Vehicles
The presence of heavy vehicles in the traffic stream decreases the FFS, because at base
conditions the traffic stream is assumed to consist only of passenger cars—a rare occurrence.
Therefore, traffic volumes must be adjusted to an equivalent flow rate expressed in passenger
cars per hour. This adjustment is accomplished by using the factor fHV.
Adjustment for the presence of heavy vehicles in the traffic stream applies to two types of
vehicles: trucks and RVs. Buses should not be treated as a separate type of heavy vehicle but
should be included with trucks. The heavy-vehicle adjustment factor requires two steps. First, the
passenger-car equivalency factors for trucks (ET) and RVs(ER) for the prevailing operating
conditions must be found. Then, using these values, an adjustment factor must be computed to
correct for all heavy vehicles in the traffic stream. Passenger-car equivalents for extended twoway segments are determined from Table 7 for estimating speeds and from Table 8 for
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
estimating percent time spent-following. The terrain of extended two-way segments should be
categorized as level or rolling.
Table 2.8: PASSENGER-CAR EQUIVALENTS FOR TRUCKS AND RVS TO DETERMINE
SPEEDS OF
TWO-WAY AND DIRECTIONAL SEGMENTS
Source: Highway Capacity Manual 2010
Table 2.9: PASSENGER-CAR EQUIVALENTS FOR TRUCKS AND RVS TO DETERMINE
PERCENT TIME-SPENT-FOLLOWING ON TWO-WAY AND DIRECTIONAL SEGMENTS
Source: Highway Capacity Manual 2010
2.11.1.6 Level Terrain
Level terrain is any combination of horizontal and vertical alignment permitting heavy vehicles
to maintain approximately the same speed as passenger cars; this generally includes short grades
of no more than 1 or 2 percent.
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
2.11.1.7 Rolling Terrain
Rolling terrain is any combination of horizontal and vertical alignment causing heavy vehicles to
reduce their speeds substantially below those of passenger cars, but not to operate at crawl
speeds for any significant length of time or at frequent intervals; generally, this includes shortand medium-length grades of no more than 4 percent. Segments with substantial lengths of more
than a 4 percent grade should be analyzed with the specific grade procedure for directional
segments. Heavy-Vehicle Adjustment Factor Once values for ET and ER have been determined,
the adjustment factor for heavy vehicles is computed using Equation 5.
(Equation 5)
Source: Highway Capacity Manual 2010
where
PT= proportion of trucks in the traffic stream, expressed as a decimal;
PR= proportion of RVs in the traffic stream, expressed as a decimal
ET= passenger-car equivalent for trucks, obtained from Table 7 or Table 8; and
ER= passenger-car equivalent for RVs, obtained from Table 7 or Table 8
2.11.1.8 Iterative Computations
Tables 5 through 8 - the grade adjustment factor fG and the passenger-car equivalents for trucks
(ET) and RVs (ER)—are stratified by flow rates expressed in passenger cars per hour. However,
until Equation 3 is applied, the flow rate in passenger cars per hour is not known. Therefore, an
iterative approach must be applied to determine the passenger-car equivalent flow rate vp, and
from that, either average travel speed or percent time-spent-following.
First, determine the flow rate, in vehicles per hour, as V/PHF. Second, select values of fG, ET,
and ER appropriate for that flow rate from the tables. Then, determine the vp from those values
using Equations 3 and 5. If the computed value of vp is less than the upper limit of the selected
flow-rate range for which fG, ET, and ER were determined, then the computed value of vp should
be used. If the vp is higher than the upper limit of the selected flow-rate range, repeat the process
for successively higher ranges until an acceptable value of vp is found. Because the highest range
includes all flow rates greater than 1,200 pc/h in both directions of travel combined, it can be
used if a computed value exceeds the upper limit of both lower flow-rate ranges.
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
2.11.1.9 Determining Average Travel Speed
The average travel speed is estimated from the FFS, the demand flow rate, and an adjustment
factor for the percentage of no-passing zones. The demand flow rate for estimating average
travel speed is determined with Equation 3 using the value of f HV computed with the passengercar equivalents in Table 7. Average travel speed is then estimated using Equation 6.
(Equation 6)
Source: Highway Capacity Manual 2010
where
ATS = average travel speed for both directions of travel combined (km/h),
fnp = adjustment for percentage of no-passing zones (see Table 9), and
vp = passenger-car equivalent flow rate for peak 15-min period (pc/h).
The FFS used in Equation 6 is the value estimated with Equation 2. The adjustment for the effect
of the percentage of no-passing zones on average travel speed (fnp) is listed in Table 9. The table
shows that the effect of no-passing zones on average travel speed increases to a maximum at a
two-way flow rate of 400 pc/h and then decreases at higher volumes. The maximum value of fnp
is 7.3 km/h.
Page 27
PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
Table 2.10: ADJUSTMENT (fnp) FOR EFFECT OF NO-PASSING ZONES ON AVERAGE
TRAVEL SPEED ON TWO-WAY SEGMENTS
Source: Highway Capacity Manual 2010
2.11.1.10 Determining Percent Time-Spent-Following
The percent time-spent-following is estimated from the demand flow rate, the directional
distribution of traffic, and the percentage of no-passing zones. The demand flow rate (vp) for
estimating percent time-spent-following is determined with Equation 3 using the value of fHV
computed with passenger-car equivalents from Table 8. Percent time-spent-following is then
estimated using Equation 7. Appropriate values of base percent time-spent-following can be
determined from Equation 8.
(Equation 7)
Source: Highway Capacity Manual 2010
where
PTSF = percent time-spent-following,
Page 28
PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
BPTSF = base percent time-spent-following for both directions of travel combined (use
Equation……..), and
fd/np = adjustment for the combined effect of the directional distribution of traffic and of
the percentage of no-passing zones on percent time-spent following
(Equation 8)
Source: Highway Capacity Manual 2010
An adjustment representing the combined effect of directional distribution of traffic and
percentage of no-passing zones (fd/np) is presented in Table 10
Table 2.11: ADJUSTMENT (fd/np) FOR COMBINED EFFECT OF DIRECTIONAL
DISTRIBUTION OF TRAFFIC AND PERCENTAGE OF NO-PASSING ZONES ON
PERCENT TIME-SPENT-FOLLOWING ON
TWO-WAYSEGMENTS
Source: Highway Capacity Manual 2010
Page 29
PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
Source: Highway Capacity Manual 2010
2.11.2 Determining LOS
The first step in determining LOS is to compare the passenger-car equivalent flow rate (vp) to the
two-way capacity of 3,200 pc/h. If vp is greater than the capacity, then the roadway is
oversaturated and the LOS is F. Similarly, if the demand flow rate in either direction of travel—
as determined from the two-way flow rate and the directional split— is greater than 1,700 pc/h,
then the roadway is oversaturated and the LOS is F. In LOS F, percent time-spent-following is
nearly 100 percent and speeds are highly variable and difficult to estimate.
When a segment of a Class I facility has a demand less than its capacity, the LOS is determined
by locating a point on Table 4 that corresponds to the estimated percent time-spent-following and
average travel speed.
Page 30
PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
3. DATA COLLECTION
3.1 TRAFFIC VOLUME COUNT
For this study, the manual method of traffic volume counting was chosen as opposed to the automatic
method due to lack of access to automatic gadgets. The tally sheets were prepared and the counters
were acquired. For stopwatches, the data collectors used their mobile phones due to lack of proper
stopwatches. The phones were however synchronized to read the exact same time. A total of six data
collectors were engaged. All the data collectors were familiar with the purpose of the data collection.
Each of the data collectors were provided with counters and instructed to record a certain class of
vehicles. Three data collectors were allocated for each direction of the road. The data collection
started at 7.00 am and ended at 7.00 pm. The seventh data collector was the relief person in the
case of bathroom breaks and lunch breaks. He also facilitated the recording of the data during the
15 minute intervals.
The data was collected at the point shown on the map below.
Page 31
PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
Map Showing data collection point.
Source: Google Earth
3.2 SPEED COUNT
The speed count was done by the moving observer method. This method involves the observer
driving along the desired length to be studied and measuring the time it takes to cover the
distance. From this time measurement, the average travelling speed can be obtained.
For this study, a total of five runs were made along the whole distance of the Eastern bypass. A
run in this case indicates a to and fro drive, from the Thika Road junction all the way to the
Page 32
PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
Kangundo Road junction, and then driving back. The time taken to drive one direction was
recorded as well as the time taken to drive back.
The speed count was carried out during different times of the day. The times were selected to
coincide with the expected peak and off peak periods. This was chosen to be able to assess the
different conditions of the road at different times of the day. This would therefore provide a good
measure of the average travel speed.
Page 33
PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
4. RESULTS AND ANALYSIS
4.1 RESULTS
4.1.1 TRAFFIC COUNT RESULTS
The following were the results obtained from the field data collection.
Table 4.1: Traffic volume counts headed to Kangundo Road
Traffic Volume Count Sheet
Approaching From: THIKA ROAD
Vehicle
Type/ Hour
Starting
7:00 AM
8:00 AM
9:00 AM
10:00 AM
11:00 AM
12:00 PM
1:00 PM
Exiting to: KANGUNDO ROAD
Motorcycles
2
Cars
97
Pickups,
Jeeps,
Vans,
SUVs
37
1
110
37
12
0
10
21
14
7
1
97
30
8
1
10
14
20
9
2
89
27
6
2
6
20
12
8
3
99
20
7
0
8
17
16
6
2
112
21
4
0
3
23
18
12
1
68
23
11
0
1
41
21
7
0
57
28
7
1
4
21
23
6
0
58
19
8
1
7
33
21
9
2
43
23
7
0
1
19
19
7
3
71
21
12
1
1
27
12
6
1
49
35
4
0
2
14
8
7
1
39
30
6
0
0
27
19
13
1
37
23
7
0
3
36
14
14
2
29
16
8
2
2
47
16
3
1
33
22
7
1
4
30
12
1
3
41
31
7
0
1
26
13
7
0
30
33
6
0
0
14
12
6
1
30
16
4
0
2
17
6
4
2
33
12
2
0
0
23
12
2
1
37
21
15
0
1
27
21
9
1
21
19
9
0
3
31
13
7
0
20
23
10
1
2
30
21
8
1
22
27
12
0
1
30
14
6
3
20
42
20
0
4
27
16
7
1
39
23
12
0
3
16
12
12
5
57
24
6
2
2
29
27
4
Matatus &
Minibuses
12
Buses
1
Light
Trucks
21
Medium
Trucks
42
Heavy
Trucks
20
6 Axle and
Drawback
Trucks
8
Page 34
PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
2:00 PM
3:00 PM
4:00 PM
5:00 PM
6:00 PM
1
60
28
8
2
0
35
19
3
3
43
21
7
0
1
42
20
7
1
33
20
12
0
0
47
21
9
2
41
31
14
0
1
31
14
6
1
29
14
8
0
3
37
12
4
3
27
23
7
1
4
26
6
3
4
28
21
6
0
7
20
14
3
2
27
14
12
0
12
16
12
7
0
29
28
7
0
10
22
13
4
1
33
23
8
0
4
37
6
2
3
37
23
10
0
7
31
12
0
1
42
25
7
1
13
20
14
7
1
41
19
12
1
6
14
6
3
2
49
27
10
0
4
13
7
6
0
63
29
12
1
8
12
12
5
1
70
33
18
0
6
16
13
4
1
97
35
12
2
10
20
12
3
3
103
61
13
2
13
21
10
1
4
102
42
16
0
12
20
23
7
1
113
39
10
1
13
33
22
6
3
97
30
14
1
10
37
16
7
Medium
Trucks
Heavy
Trucks
6 Axle and
Drawback
Trucks
Table 4.2: Traffic Volume Counts headed to Thika Road
Traffic Volume Count Sheet
Approaching From: KANGUNDO ROAD
Vehicle
Type/ Hour
Starting
7:00 AM
8:00 AM
9:00 AM
Exiting to: THIKA ROAD
Motorcycles
Cars
Pickups,
Jeeps,
Vans,
SUVs
3
154
69
22
2
23
27
21
10
0
127
53
16
3
11
33
20
3
1
136
59
18
1
12
21
14
4
2
113
48
12
0
10
30
22
8
2
110
57
19
1
11
24
12
7
3
121
96
12
2
17
22
16
6
5
97
41
8
3
14
29
22
8
2
101
41
10
0
12
20
24
3
4
86
46
6
1
9
22
13
1
2
54
49
12
0
10
17
27
7
1
91
39
10
0
6
29
14
4
Matatus &
Minibuses
Buses
Light
Trucks
Page 35
PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
10:00 AM
11:00 AM
12:00 PM
1:00 PM
2:00 PM
3:00 PM
4:00 PM
5:00 PM
6:00 PM
2
84
40
8
0
3
30
18
3
0
61
39
7
1
5
33
26
1
1
41
37
7
0
2
41
21
2
0
48
41
4
0
1
26
12
1
2
36
35
6
0
4
13
14
1
1
41
34
1
0
3
27
16
4
1
37
39
3
0
1
40
21
3
2
39
29
5
1
0
31
14
9
2
53
30
4
0
0
33
12
7
1
54
37
5
0
1
42
20
8
3
46
31
1
0
3
53
21
6
1
44
24
6
0
2
41
16
4
2
48
38
4
1
1
40
12
6
1
63
42
7
0
1
30
22
7
1
54
51
1
0
6
29
31
8
3
68
48
3
0
3
48
12
12
1
57
60
5
1
4
44
23
6
4
49
47
2
1
3
31
27
7
1
51
33
1
0
1
27
14
7
2
53
40
1
0
1
20
28
11
2
47
31
0
1
2
22
28
3
0
57
27
3
0
1
22
27
2
1
48
31
5
1
0
19
23
5
1
50
20
1
0
0
20
20
5
3
60
14
1
0
5
24
27
6
3
58
16
0
0
6
39
30
5
3
56
20
2
0
1
44
19
4
2
61
12
3
0
4
37
16
0
1
73
21
3
0
0
41
12
1
3
77
22
5
0
3
40
14
2
4
82
46
7
0
4
39
16
1
4
107
51
9
1
3
41
21
3
5
100
39
13
2
1
32
21
4
1
110
57
6
0
1
27
20
4
5
137
52
7
2
4
31
18
6
3
126
41
9
1
2
29
30
8
1
112
60
10
1
1
19
20
8
The following are the corrected values of the traffic counts in Passenger Car Units. The
correction factors used are as outlined in the literature review.
Page 36
PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
Table 4.3: Corrected PCU Values for the traffic count headed to Kangundo Road
Traffic Volume Count Sheet
Approaching From: THIKA ROAD
7:00 AM - 7:15 AM
7:15 AM - 7:30 AM
7:30 AM - 7:45 AM
7:45 AM - 8:00 AM
8:00 AM - 8:15 AM
8:15 AM - 8:30 AM
8:30AM - 8:45 AM
8:45 AM - 9:00 AM
9:00 AM - 9:15 AM
9:15 AM - 9:30 AM
9:30AM - 9:45 AM
9:45 AM - 10:00 AM
10:00 AM - 10:15 AM
10:15 AM - 10:30 AM
10:30 AM - 10:45 AM
10:45 AM - 11:00 AM
11:00 AM - 11:15 AM
11:15 AM - 11:30 AM
11:30 AM - 11:45 AM
11:45 AM - 12:00 PM
12:00 PM - 12:15 PM
12:15 PM - 12:30 PM
12:30 PM - 12:45 PM
12:45 PM - 1:00 PM
1:00 PM - 1:15 PM
1:15 PM - 1:30 PM
1:30 PM - 1:45 PM
1:45 PM - 2:00 PM
2:00 PM - 2:15 PM
2:15 PM - 2:30 PM
2:30 PM - 2:45 PM
2:45 PM - 3:00 PM
3:00 PM - 3:15 PM
3:15 PM - 3:30 PM
3:30 PM - 3:45 PM
3:45 PM - 4:00 PM
4:00 PM - 4:15 PM
4:15 PM - 4:30 PM
4:30 PM - 4:45 PM
4:45 PM - 5:00 PM
5:00 PM - 5:15 PM
Exiting to: KANGUNDO ROAD
Corrected PCU
Values for
Motorcycles
Corrected PCU
Values for SUVs
/pickups, matatus
/minibuses
Corrected PCU
Values for buses
Corrected
PCU Values
for Trucks
0.66
0.33
0.33
0.66
0.99
0.66
0.33
0
0
0.66
0.99
0.33
0.33
0.33
0.66
0.33
0.99
0
0.33
0.66
0.33
0.33
0
0.33
0.99
0.33
1.65
0.33
0.99
0.33
0.66
0.33
0.99
1.32
0.66
0
0.33
0.99
0.33
0.33
0.66
98
98
76
66
54
50
68
70
54
60
66
78
72
60
48
58
76
78
40
28
72
56
66
78
124
70
60
72
56
64
90
44
60
54
52
70
62
66
64
62
74
2.5
0
2.5
5
0
0
0
2.5
2.5
0
2.5
0
0
0
5
2.5
0
0
0
0
0
0
2.5
0
0
0
5
5
0
0
0
0
2.5
0
0
0
0
0
2.5
2.5
0
273
156
159
138
141
168
210
162
210
138
138
93
177
201
204
141
141
96
87
111
174
162
183
153
162
129
186
171
210
231
156
168
117
132
141
147
147
150
162
87
90
Page 37
PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
5:15 PM - 5:30 PM
5:30 PM - 5:45 PM
5:45 PM - 6:00 PM
6:00 PM - 6:15 PM
6:15 PM - 6:30 PM
6:30 PM - 6:45 PM
6:45 PM - 7:00 PM
0
0.33
0.33
0.99
1.32
0.33
0.99
82
102
94
148
116
98
88
2.5
0
5
5
0
2.5
2.5
111
117
135
135
186
222
210
Table 4.4: Corrected PCU Values for the traffic count headed to Thika Road
Traffic Volume Count Sheet
Exiting to: THIKA ROAD
Approaching From: KANGUNDO ROAD
7:00 AM - 7:15 AM
7:15 AM - 7:30 AM
7:30 AM - 7:45 AM
7:45 AM - 8:00 AM
8:00 AM - 8:15 AM
8:15 AM - 8:30 AM
8:30AM - 8:45 AM
8:45 AM - 9:00 AM
9:00 AM - 9:15 AM
9:15 AM - 9:30 AM
9:30AM - 9:45 AM
9:45 AM - 10:00 AM
10:00 AM - 10:15 AM
10:15 AM - 10:30 AM
10:30 AM - 10:45 AM
10:45 AM - 11:00 AM
11:00 AM - 11:15 AM
11:15 AM - 11:30 AM
11:30 AM - 11:45 AM
11:45 AM - 12:00 PM
12:00 PM - 12:15 PM
12:15 PM - 12:30 PM
12:30 PM - 12:45 PM
12:45 PM - 1:00 PM
1:00 PM - 1:15 PM
1:15 PM - 1:30 PM
1:30 PM - 1:45 PM
1:45 PM - 2:00 PM
2:00 PM - 2:15 PM
2:15 PM - 2:30 PM
2:30 PM - 2:45 PM
2:45 PM - 3:00 PM
Corrected PCU
Values for
Motorcycles
Corrected PCU
Values for SUVs
/pickups, matatus
/minibuses
Corrected PCU
Values for
buses
Corrected
PCU Values
for Trucks
0.99
0
0.33
0.66
0.66
0.99
1.65
0.66
1.32
0.66
0.33
0.66
0
0.33
0
0.66
0.33
0.33
0.66
0.66
0.33
0.99
0.33
0.66
0.33
0.33
0.99
0.33
1.32
0.33
0.66
0.66
182
138
154
120
152
216
98
102
104
122
98
96
92
88
90
82
70
84
68
68
84
64
60
84
98
104
102
130
98
68
82
62
5
7.5
2.5
0
2.5
5
7.5
0
2.5
0
0
0
2.5
0
0
0
0
0
2.5
0
0
0
0
2.5
0
0
0
2.5
2.5
0
0
2.5
243
201
153
210
162
183
219
177
135
183
159
162
195
198
120
96
150
195
162
156
213
249
189
177
180
222
225
231
204
147
180
165
Page 38
PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
3:00 PM - 3:15 PM
3:15 PM - 3:30 PM
3:30 PM - 3:45 PM
3:45 PM - 4:00 PM
4:00 PM - 4:15 PM
4:15 PM - 4:30 PM
4:30 PM - 4:45 PM
4:45 PM - 5:00 PM
5:00 PM - 5:15 PM
5:15 PM - 5:30 PM
5:30 PM - 5:45 PM
5:45 PM - 6:00 PM
6:00 PM - 6:15 PM
6:15 PM - 6:30 PM
6:30 PM - 6:45 PM
6:45 PM - 7:00 PM
0
0.33
0.33
0.99
0.99
0.99
0.66
0.33
0.99
1.32
1.32
1.65
0.33
1.65
0.99
0.33
60
72
42
30
32
44
30
48
54
106
120
104
126
118
100
140
0
2.5
0
0
0
0
0
0
0
0
2.5
5
0
5
2.5
2.5
156
141
135
186
240
204
171
162
177
180
204
174
156
177
207
144
The average 15 minute traffic was as depicted below:
Table 4.5: Average 15 minute traffic headed to Kangundo Road
Approaching From: THIKA ROAD
Time
7:00 AM - 7:15 AM
7:15 AM - 7:30 AM
7:30 AM - 7:45 AM
7:45 AM - 8:00 AM
8:00 AM - 8:15 AM
8:15 AM - 8:30 AM
8:30AM - 8:45 AM
8:45 AM - 9:00 AM
9:00 AM - 9:15 AM
9:15 AM - 9:30 AM
9:30AM - 9:45 AM
9:45 AM - 10:00 AM
10:00 AM - 10:15 AM
10:15 AM - 10:30 AM
10:30 AM - 10:45 AM
10:45 AM - 11:00 AM
11:00 AM - 11:15 AM
11:15 AM - 11:30 AM
Exiting to: KANGUNDO
ROAD
Average 15 min Traffic
471.16
364.33
334.83
298.66
294.99
330.66
346.33
291.5
324.5
241.66
278.49
220.33
288.33
298.33
286.66
234.83
258.99
204
Page 39
PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
11:30 AM - 11:45 AM
11:45 AM - 12:00 PM
12:00 PM - 12:15 PM
12:15 PM - 12:30 PM
12:30 PM - 12:45 PM
12:45 PM - 1:00 PM
1:00 PM - 1:15 PM
1:15 PM - 1:30 PM
1:30 PM - 1:45 PM
1:45 PM - 2:00 PM
2:00 PM - 2:15 PM
2:15 PM - 2:30 PM
2:30 PM - 2:45 PM
2:45 PM - 3:00 PM
3:00 PM - 3:15 PM
3:15 PM - 3:30 PM
3:30 PM - 3:45 PM
3:45 PM - 4:00 PM
4:00 PM - 4:15 PM
4:15 PM - 4:30 PM
4:30 PM - 4:45 PM
4:45 PM - 5:00 PM
5:00 PM - 5:15 PM
5:15 PM - 5:30 PM
5:30 PM - 5:45 PM
5:45 PM - 6:00 PM
6:00 PM - 6:15 PM
6:15 PM - 6:30 PM
6:30 PM - 6:45 PM
6:45 PM - 7:00 PM
157.33
172.66
283.33
239.33
271.5
253.33
306.99
238.33
309.65
308.33
309.99
328.33
287.66
241.33
207.49
215.32
220.66
246
242.33
253.99
270.83
192.83
213.66
258.5
289.33
331.33
391.99
405.32
435.83
398.49
Table 4.6: Average 15 minute traffic headed to Thika Road
Approaching from: KANGUNDO
ROAD
Exiting to: THIKA ROAD
Time
7:00 AM - 7:15 AM
7:15 AM - 7:30 AM
7:30 AM - 7:45 AM
7:45 AM - 8:00 AM
8:00 AM - 8:15 AM
8:15 AM - 8:30 AM
Average 15 min Traffic
584.99
473.5
445.83
443.66
427.16
525.99
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
8:30AM - 8:45 AM
8:45 AM - 9:00 AM
9:00 AM - 9:15 AM
9:15 AM - 9:30 AM
9:30AM - 9:45 AM
9:45 AM - 10:00 AM
10:00 AM - 10:15 AM
10:15 AM - 10:30 AM
10:30 AM - 10:45 AM
10:45 AM - 11:00 AM
11:00 AM - 11:15 AM
11:15 AM - 11:30 AM
11:30 AM - 11:45 AM
11:45 AM - 12:00 PM
12:00 PM - 12:15 PM
12:15 PM - 12:30 PM
12:30 PM - 12:45 PM
12:45 PM - 1:00 PM
1:00 PM - 1:15 PM
1:15 PM - 1:30 PM
1:30 PM - 1:45 PM
1:45 PM - 2:00 PM
2:00 PM - 2:15 PM
2:15 PM - 2:30 PM
2:30 PM - 2:45 PM
2:45 PM - 3:00 PM
3:00 PM - 3:15 PM
3:15 PM - 3:30 PM
3:30 PM - 3:45 PM
3:45 PM - 4:00 PM
4:00 PM - 4:15 PM
4:15 PM - 4:30 PM
4:30 PM - 4:45 PM
4:45 PM - 5:00 PM
5:00 PM - 5:15 PM
5:15 PM - 5:30 PM
5:30 PM - 5:45 PM
5:45 PM - 6:00 PM
6:00 PM - 6:15 PM
6:15 PM - 6:30 PM
6:30 PM - 6:45 PM
423.15
380.66
328.82
359.66
348.33
342.66
350.5
327.33
258
214.66
261.33
316.33
272.16
277.66
351.33
359.99
293.33
312.16
341.33
380.33
395.99
420.83
354.82
266.33
315.66
277.16
273
263.83
227.33
276.99
330.99
304.99
262.66
283.33
308.99
369.32
434.82
384.65
392.33
438.65
436.49
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
6:45 PM - 7:00 PM
398.83
The average hourly traffic was as depicted below.
Table 4.7: Average Hourly Traffic Headed to Kangundo Road
Time
Exiting To: KANGUNDO
ROAD
Hourly Traffic
7:00 AM
1468.98
8:00 AM
1263.48
9:00 AM
1064.98
10:00 AM
1108.15
11:00 AM
792.98
12:00 PM
1047.49
1:00 PM
1163.3
2:00 PM
1167.31
3:00 PM
889.47
4:00 PM
959.98
5:00 PM
1092.82
6:00 PM
1631.63
TOTAL TRAFFIC
13,651
Approaching from: THIKA ROAD
Table 4.8: Hourly Traffic counts headed to Thika Road
Approaching From: KANGUNDO
ROAD
Time
Exiting To: THIKA ROAD
Hourly Traffic
7:00 AM
1947.98
8:00 AM
1756.96
9:00 AM
1379.47
10:00 AM
1150.49
11:00 AM
1127.48
12:00 PM
1316.81
1:00 PM
1538.48
2:00 PM
1213.97
3:00 PM
1041.15
4:00 PM
1181.97
5:00 PM
1497.78
6:00 PM
1666.3
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
TOTAL TRAFFIC
16,819
The Directional Split was as depicted below.
Table 4.9: Directional Split
TO KANGUNDO
ROAD
13650.57
44.80%
TO THIKA ROAD
16818.84
55.20%
4.1.2 SPEED COUNT RESULTS
Table 4.10: Speed Counts for both directions
Run
No.
1
2
3
4
5
Distance
(KM)
13.75
13.75
13.75
13.75
13.75
Time of
Run
7:10 AM
10:30 AM
1:20 PM
3:30 PM
5:30 PM
Time Taken
To (Mins &
Secs)
14 min 44s
9 min 10s
13 min 5s
10 min 43s
13 min 58s
Speed Count Sheet
Time
Time
Taken Fro Taken
(Mins &
To
Secs)
(Hrs)
16 min 30s 0.246
10 min 02s 0.153
12 min 41s 0.218
11 min 56s 0.179
15 min 44s 0.233
Time
Taken
Fro
(Hrs)
0.275
0.167
0.211
0.199
0.262
Average
Speed
To
55.89431
89.86928
63.07339
76.81564
59.01288
Average
Speed Fro
50
82.335329
65.165877
69.095477
52.480916
Average
Run
Speed
52.94715
86.10231
64.11964
72.95556
55.7469
TOTAL
AVERAG
E SPEED
66.37431
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
4.2 ANALYSIS
Figure 4.1 : Graph of Number of Different Classes of Vehicles headed to Kangundo Road
Number of Different Vehicle Classes
3000
2500
Number
2000
1500
1000
500
0
Number
Motorcycl
es
Cars
79
2602
Pick ups,
Matatus
Jeeps,
&
Vans,
Minibuses
SUVs
1269
452
Buses
Light
Trucks
Medium
Trucks
Heavy
Trucks
6 Axle
and
Drawback
Trucks
25
246
1252
716
292
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
Figure 4.2: Graph of Numbers of Different Classes of Vehicles Headed to Thika Road
Number of Different Vehicle Classes
4000
3500
3000
Number
2500
2000
1500
1000
500
0
Number
Motorcyc
les
Cars
Pick ups,
Jeeps,
Vans,
SUVs
98
3578
1933
Matatus
&
Minibuse
s
Buses
Light
Trucks
Medium
Trucks
Heavy
Trucks
6 Axle
and
Drawback
Trucks
310
27
218
1479
947
241
Number
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
Figure 4.3: Graph Of Average 15 Min Traffic Approaching from Thika Road and Exiting to
Kangundo Road
Average 15 min Traffic
500
450
400
350
300
250
200
150
100
50
0
Observation: The graph depicts the different shifts in the 15 minutes traffic. It shows the rise in
the traffic counts during the expected peak hours of the day. The highest 15 minute traffic is that
between 7:00 AM and 7:15 AM. This represents the main period when most people are headed
to their places of work. It is higher because most people leave their houses early in order to beat
the traffic pile ups.
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
Figure 4.4: Graph Of Average 15 Min Traffic Approaching from Kangundo Road and Exiting to
Thika Road
Average 15 min Traffic
700
600
500
400
300
200
100
0
Observation: This shows a similar trend on the way towards Thika Superhighway, only that this
time the traffic numbers are higher. This is because most people work within the city and the
quickest way to get there is by use of the Thika Superhighway. The high number of motor
vehicles is also contributed to by the high number of trucks bypassing the busy Mombasa Road.
Most are travelling at these morning hours after having spent the night at a place known as
Mlolongo along Mombasa Road.
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
Figure 4.5: Graph Of Average Hourly Traffic Approaching from Thika Road and Exiting to
Kangundo Road
Hourly Traffic
2200
2000
1800
1600
1400
1200
1000
Hourly Traffic
800
600
400
200
0
7:00
AM
8:00
AM
9:00
AM
10:00 11:00 12:00
AM
AM
PM
1:00
PM
2:00
PM
3:00
PM
4:00
PM
5:00
PM
6:00
PM
Observation: The graph clearly shows the peak hours for the day. From the results, there are
mainly three peak periods where the peak hour is. These are 7:00 AM - 8:00 AM, 12:30 PM –
1:30 PM, and 6:00 PM – 7:00 PM. It also shows the off-peak periods, which are 10:00 AM to
11:00 AM and 2:30 PM - 3:30 PM.
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
Figure 4.6: Graph Of Average Hourly Traffic Approaching from Kangundo Road and Exiting to
Thika Road
Hourly Traffic
1800
1600
1400
1200
1000
800
Hourly Traffic
600
400
200
0
7:00
AM
8:00
AM
9:00
AM
10:00 11:00 12:00
AM
AM
PM
1:00
PM
2:00
PM
3:00
PM
4:00
PM
5:00
PM
6:00
PM
Observation: Similarly, this graph shows the peak hours for the day which are also three in
number. These are 7:00 AM - 8:00 AM, 1:00 PM – 2:00 PM, and 5:30 PM – 6:30 PM. It also
shows the off-peak periods, which are 10:30 AM to 11:30 AM and 2:30 PM - 3:30 PM.
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
Figure 4.7: Pie Chart Showing Directional Split Between The Two Directions
TO KANGUNDO ROAD
TO THIKA ROAD
4.3 DETERMINING LEVEL OF SERVICE OF THE ROAD.
4.3.1 Determining free flow speed.
The free flow speed was determined for a capacity of more than 200pc/h. Therefore the FFS is
determined as thus.
FFS = estimated free-flow speed (km/h),
SFM = mean speed of traffic measured in the field (km/h) = 66.37
Vf = observed flow rate for the period when field data were obtained (veh/h)
= 1948 veh/h
fHV = heavy-vehicle adjustment factor, determined as shown below
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
where
PT= proportion of trucks in the traffic stream, expressed as a decimal;
PR= proportion of RVs in the traffic stream, expressed as a decimal
ET= passenger-car equivalent for trucks, obtained from Table 7 or Table 8; and
ER= passenger-car equivalent for RVs, obtained from Table 7 or Table 8
From: THIKA ROAD
To: KANGUNDO ROAD
Table 4.11: Proportion of Trucks and RVs headed to Kangundo Road
Total
Unfactored
Vehicles
Total
Unfactored
RVs
6933
From: THIKA ROAD
1721
Total
Unfactored
Trucks
2506
To: KANNGUNDO ROAD
Table 4.12: Proportion of Trucks and RVs headed to Thika Road
Total
Unfactored
Vehicles
PT =
Total
Unfactored
RVs
8831
2506+2885
6933+8831
PR =
2243
Total
Unfactored
Trucks
2885
= 0.342
1721+2243
6933+8831
= 0.251
ET = 1.0 (Table 8)
ER = 1.0 (Table 8)
fHV =
1
1+0.342(1.0−1)+ 0.251 (1.0−1)
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
fHV = 1
Therefore, FFS = 66.37 + 0.0125
1948
1
= 66.37 + 24.35
= 90.72 km/h
4.3.2 Determining Demand Flow Rate
The demand flow rate is determined using the formula below.
where
vp = passenger-car equivalent flow rate for peak 15-min period (pc/h),
V = demand volume for the full peak hour (veh/h) = 1948 veh/h
PHF = peak-hour factor,
fG = grade adjustment factor, and
fHV = heavy-vehicle adjustment factor determined as shown in Equation 5
𝑉
𝑃𝐻𝐹 =
𝑉15 𝑋 4
Where:
PHF = Peak Hour Factor
V = Hourly volume (veh/h) = 1948 veh/h
V15 = Maximum 15 minute rate of flow = 585 veh
1948
PHF =
585 𝑋 4
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
= 0.8325
fG = 1 (Table 5)
fHV = 1
Vp =
1948
0.8325 𝑋 1 𝑋 1
vp = 2339.93
= 2340 pc/h
4.3.3 Determining The Average Travel Speed
where
ATS = average travel speed for both directions of travel combined (km/h),
FFS = Free Flow Speed (km/h) = 90.72 km/h
fnp = adjustment for percentage of no-passing zones (see Table 9), and
vp = passenger-car equivalent flow rate for peak 15-min period (pc/h) = 2340
fnp
Total distance = 13.75km
No passing zone Distance = 1.4 km
Percentage no passing zone =
1.4
13.75
𝑋 100 = 10.18%
fnp = 0.4 (Interpolated from Table 9)
ATS = 90.72 – 0.0125(2340) – 0.4
= 61.07 km/h
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
4.3.4 Determining Percent Time Spent Following
The percent time spent following is determined by the equation below:
where
PTSF = percent time-spent-following,
BPTSF = base percent time-spent-following for both directions of travel combined
fd/np = adjustment for the combined effect of the directional distribution of traffic and of
the percentage of no-passing zones on percent time-spent following
BPTSF = 100 (1 - 𝑒 −0.000879 (2340) )
= 87.185
fd/np = 0.8 (Interpolated from Table 10)
PTSF = 87.185+0.8 = 87.98%
4.3.5 Determining Level Of Service
With the Average speed at 61.07 km/h and the Percentage Time Spent Following at 87.98
%, the level of service of Nairobi Eastern Bypass can now be determined from the diagram
below.
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
Figure 4.8: Figure Showing The level of service of the Road
Source: Highway Capacity Manual 2010
The study indicates that in general, the road is operating at level of service E.
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
5. DISCUSSION
5.1 DISCUSSION ON TRAFFIC FLOW RESULTS
5.1.1 MORNING TRAFFIC
5.1.1.1 Thika Road bound traffic
It was observed that this was the highest number traffic that was recorded. This can be attributed
to the high number of people trying to access the Central Business District. In spite of the road
being over 20km (Google maps) from the CBD, the accessibility of the area after the
construction of Thika Superhighway and the Eastern Bypass led to a high increase in the
population. People who owned some land along the road have developed the land into their own
homes or into establishments for entertainment. Thus the number of people dependent on the
road drastically shot up after its construction. Most of these trips are therefore Home-Based
Work trips.
The high number of vehicles can also be attributed to the high number of trucks using the road at
this time. Most of these trucks trips originated from the port of Mombasa and will terminate
somewhere in the interior of the country or into the neighboring countries. These trucks normally
make overnight stops at a center known as Mlolongo. (Appending 2) The center is only a few
kilometers from the junction of the bypass with Mombasa road. Thus the truck drivers rise early
to try and beat the morning traffic. Interviews conducted with a few truck drivers indicate that
their days start as early as 5:00 AM. This increases greatly the number of vehicles between 5 AM
and 7:30 AM.
The highest recorded number of passenger car units was 585 passenger car units for the 15
minute interval. For a two way rural highway which is designated a maximum of 1700pc/h
(HCM2010), this number has overshot its design capacity. The road ought to be operating at a
maximum of 425pcu for every 15 minutes for it to be economically sound. This is however not
the case as it operated at 38% higher than the design capacity for this particular 15 minute
period. This therefore indicates a level of service of F.
5.1.1.2 Kangundo Road Bound Traffic
It was observed that the morning traffic heading to Kangundo Road was equally high. The
numbers may have been a little lower than those of the opposing traffic, but they were still
significant. These high numbers of traffic can be attributed to the high number of people headed
towards Mombasa road from Thika Road and The Nakuru – Nairobi Highway. These are mainly
people headed to work in the industries along Mombasa Road, or to the airport. This also
comprises of people heading to the airport to catch their morning flights.
The high numbers can also be attributed to the high number of trucks in the traffic stream. These
are trucks on their return journey from the interior of the country and from the neighboring land
locked countries towards the Port of Mombasa. Most of these truck drivers spent the night along
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
the various stops along the Mai-Mahiu – Narok Road or in Thika Town. They are also trying to
beat the morning traffic and hence the early hours on the road.
In this case, the highest recorded number of pcu was 471 for a 15 minute interval. Compared
with the design average of 425pcu for every 15 minute interval, the operational capacity is still
high than the design capacity. The operational capacity is at 11% higher than the design capacity.
This indicates that the road is operating at level of service F at this particular peak period.
For both cases of the morning traffic then, the road seems to have overshot its design capacity.
The operational capacity for this particular peak morning period needs to be lowered for the road
to be economically valuable as well as operate at its design level of service.
5.1.2 EVENING TRAFFIC
5.1.2.1 Thika Road Bound Traffic
It was observed that there were high numbers of vehicles during this peak hour. This can be
attributed to people heading back to their homes after work. Most of the people headed back are
those that work along Mombasa Road industries as well as those that work at the airport. The
high number of vehicles can also be attributed to the increase in the number of trucks trying to
get to their night stop at Mlolongo before it gets dark. This greatly increases the traffic on the
road.
The highest number of vehicles recorded for a 15 minute period was 438 vehicles. Comparing
this number with the accepted average of 425pcu indicates that the road at this hour was also
operating at a greater capacity than the design capacity. It is however only 3% greater than the
design capacity. This therefore indicates a level of service F.
5.1.2.2 Kangundo Road Bound Traffic
The situation is the same for Kangundo Road traffic. There is an increase in the number of motor
vehicles on the road during this peak period as well. This is attributed mostly to the same case of
the Thika road bound traffic. The traffic flow mainly comprises of small cars and SUVs as
people head back to their homes from work. The numbers of trucks were noticeably lower than
that of the reverse traffic. Most of the truck drivers had taken their rest for the day at Mlolongo.
The highest number of motor vehicles recorded during a 15 minute period was 435 vehicles. This
was a little higher than the design values of 425pcu, but not as high as that of the morning traffic.
It was at 3% greater, thus indicating a level of service F.
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
5.1.3 MID DAY TRAFFIC
5.1.3.1 Thika Road Bound Traffic
A rise in the traffic counts was also witnessed somewhere in the middle of the day. For Thika
road bound traffic, this was between 1:00 PM and 2:00 PM. This came as a result of the number
of motorists heading for lunch along the many establishments increased. The road boasts a good
number of lunch and entertainment joints. These have become a favorite among the people who
live or work around and along the road. Some of the customers came from as far as the city
center to enjoy the delicacies at the joints. The increased number of vehicles accessing the turnoffs and accesses to these establishment not only increased the traffic numbers, but also caused
long shockwaves behind them.
In spite of an increase in the number of vehicles at this hour, the count could not match of
morning or evening hours. The highest number of vehicles recorded in this direction was 421pcu
as opposed to the design value of 425pcu for every 15 minutes. This means that the operational
capacity has not overshot the design capacity. However, at this point, the traffic is operating at
level of service E.
5.1.3.2 Kangundo Road Bound Traffic
The same case was witnessed with the traffic headed to Kangundo Road. The number of vehicles
sharply rose between 12:30 PM and 1:30 PM. This too can be attributed to the increased number
of people making use of the lunch break to run errands and go get lunch. Slowing down of
vehicles to access the joints also led to long shockwaves in the traffic stream.
In this case as well, the number of vehicles could not reach those that were witnessed in the peak
morning and evening hours. The highest number recorded was put at 328 vehicles. This
compared to the design value of 425pcu, can be said to be fairly efficient. This value however
represents a level of service D
5.1.4 OFF PEAK TRAFFIC
5.1.4.1 Thika Road Bound Traffic
The study established two basic off peak hours for the traffic stream. These were periods when
the traffic counts went low. These were witnessed at 10:30 AM – 11:00 AM and 2:30 pm – 3:30
PM. These periods can be attributed to the decline in number of passenger cars and SUVs on the
roads. Most people have settled in at their place of work. The number of trucks also reduces, but
not as significantly as the number of passenger cars.
The lowest number of vehicles recorded was 214pcu for a 15 minute period. This is a pretty good
value compared to the 425pcu design capacity of the road.(HCM2000) This represents a level of
service C, which unfortunately is still worse than the design level of service B.
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
5.1.4.2 Kangundo Road Bound Traffic
The same decline in the traffic counts was recorded in the vehicles headed to Kangundo Road.
There were two off peak periods recorded. In this case they were between 10:30 AM – 11:30
AM and 2:30 PM – 3:30 PM. These two periods can also be attributed to the decline in the
number of passenger cars and SUVs from the traffic stream.
The lowest number of vehicles recorded was 158pcu in a 15 minute period. This is a fairly low
number. It represents a level of service C. This therefore means that the road was also
performing worse than its design value.
5.2 DISCUSSION ON SPEED-FLOW RESULTS
The results on the speed counts indicate a high fluctuation in the travel speeds of vehicles along
the Nairobi Eastern Bypass. The speeds mainly vary depending on the number of vehicles on the
road. This means that different peak periods experience different travel speeds. The speed count
was purposely run on the peak and off peak periods in order to establish a good average run
speed.
The morning high capacity on the road indicates the lowest speeds experienced. The lowest
speed was recorded at 52.94km/h. This is a very low value compared with the free flow speed of
approximately 90.72km/h. This means that some mitigation measures need to be taken to enable
traffic operate more efficiently.
The highest speeds were recorded during the off peak period. During the morning peak period,
the highest speed was put at 86.10km/h. This speed is fairly close to the free flow speed of
90.72km/h. Thus the road was found to be performing fairly well during the off peak periods.
In spite of determining the average speed for one day, it can be considered fairly accurate to the
daily operation speeds. Spot speeds determined earlier indicate a similar value for the travel
speed. The average speed value therefore determined was a fairly correct value
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
6. CONCLUSION
6.1 CAPACITY AND LEVEL OF SERVICE
The highway capacity manual(HCM2010) puts the design capacity of a two way, two lane rural
highway at 3400pcu/h, or 1700pcu/h in each direction. The study established the operational
capacity for the peak 15 minute period in passenger-car equivalents to be 2340pcu/h. Therefore it
can be established that the Nairobi Eastern Bypass has overshot its design capacity by more than
37%.
The Kenya Roads Board(KRB) website indicates that the Eastern Bypass was designed to
operate at level of service B. This study however established that the road is operating at Level
of Service E. The road therefore is underperforming.
From the above two parameters determined from the Eastern Bypass, it can be concluded that a
lot needs to be done on the road to alleviate the poor performance. Some changes have to be
effected on the road to increase the efficiency of the road. Such poor driving conditions also
increase the drivers discomfort on the road and may lead to frustrations. This may cause an
increase in the rate of accidents as drivers to overtake vehicles.
In the beginning, this study set out to determine the operational capacity as well as the level of
service of the Nairobi Eastern Bypass. The necessary measures required to conduct this study
were adhered to and the data collected enabled the study to determine the capacity of the road
and hence its operational level of service. Therefore the objectives of the study were achieved.
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
7. RECOMMENDATIONS
Improvement of the operational characteristics of transportation facilities is important for the
following benefits:
Reduction in Vehicle Operational Costs,
Saving on the time spent on the roads.
Reduction in the frequency of accidents
With a high growth rate not only in the population but also in the number of motor vehicles
accessing our roads, it is important that an effort be made to improve the efficiency of the
existing facilities.
The main challenge along the Nairobi Eastern Bypass was determined to be the high number of
vehicles using the road. This is a major challenge especially considering that the road was
designed to reduce the traffic in the city center. In terms of redirecting traffic that does not need
to access the city center away from it, the road may be considered to have achieved its purpose,
since a great number of trucks use the road now. It terms of efficiently performing its mandate,
the road may be considered to have failed in this. Therefore a number of mitigative measures
need to be undertaken to alleviate this problem.
In this case, there are mainly two mitigative measures that can be taken. These are:
Improving the infrastructure
Traffic Management
7.1 IMPROVING THE INFRASTRUCTURE
This basically entails making changes to the road to ensure efficiency of movement of the
vehicles. There are several ways of doing this:
 Converting the Eastern Bypass into a four lane two way dual carriageway
This would increase the carrying capacity of the road and enable more traffic efficiently use the
road. This would also provide the capacity for conversion of one of the lanes into a trucks only
lane. It would also give provision for overtaking of the slow trucks.
 Provision of passing lanes at regular intervals
Passing lanes could be introduced on the road to facilitate the ability of small vehicles to
overtake slow moving trucks. The passing lanes can be introduced at regular intervals on both
directions of the road, for example after every three kilometers, 500 meters of passing lane is
provided. This would lead to a higher efficiency of the road.
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
7.2 TRAFFIC MANAGEMENT
This entails systematically controlling traffic by imposing regulatory measures and enforcing
management techniques that make most economic use of the road. Some of the traffic
management measures include:
 Discouraging use of private vehicles and encouraging use of public transport amenities
This may be a very helpful measure in reducing the number of private vehicles on the road,
which comprise the greatest percentage of vehicles on the road. These measures may be enforced
by:


Road Pricing
This means charging private vehicles a fee for using the road. This would make the
number of vehicles accessing the road reduce. The modal shift would change and more
people would opt for public means of travel.
Improvement of public transport.
The modes of public transport should be improved and made more efficient and timely,
so as to entice their use by the public. The public transport vehicles should be made more
habitable and timely. They should also be made more affordable to attract their use by the
public.
 Carpooling
This is the sharing of private cars by people living in the same area to and from work to
reduce the number of cars on the roads. People using the road to get to the city center in
the morning to work and leave in the evening should be encouraged to share their
vehicles.
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PERFOMANCE ANALYSIS OF EASTERN BYPASS 2015
8. LIST OF REFERENCES
1. Kane, Tony. “Opening Session Welcome” in Performance Measures to Improve
Transportation Systems: Summary of the Second National Conference. National Academy Press,
Washington, D.C., 2005.
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9. APPENDICES
1. Map showing Mlolongo Truck Overnight Stop.
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2. Photo showing some of the data collectors
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3. Photo showing a shockwave caused by a slow moving truck
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