Question One
a) Table Q1(a) shows vehicle time and space headways measured at a point along a
highway during a spot speed and volume survey. By use of this tabulated data, and given
that 1 mile is equivalent to 5280 ft, determine the maximum flow by Greenberg model
from first principles.
(24marks)
Table Q1(a)
AVERAGE TIME HEADWAY (s/veh)
3.383
2.772
2.296
2.040
1.856
1.763
1.760
2.068
2.521
2.743
3.007
3.053
3.214
3.913
AVERAGE SPACING (ft/veh)
264.000
195.556
116.000
120.000
101.538
91.034
88.000
82.500
75.429
70.400
64.390
58.667
52.800
45.913
b) A state transportation agency has established crash reduction factors as shown in Table
Q1(b). An intersection has been identified as having an abnormally high left turn crash
rate of 17, 20 and 18 crashes in the last three years, attributed to excessive speeds and the
absence of an exclusive left turn phase. The ADT of the intersection for the last three
years is 8400, and the ADT for after implementation is 9500. Determine the expected
reduction in the crashes if the tabulated countermeasures are implemented (6marks)
Table Qb(b)
Countermeasure
Reduction
Retime signals
0.10
Provide left turn signal phase
0.30
Reduce speed limit on approaches
0.35
Provide turning guidelines
0.05
1
Prohibit left turns
0.75
Question Two
a) Table Q2 shows data obtained in a travel time study on a section of a 3.5km section of a
highway, by the moving – observer method, using a high precision radar gun. If
ordinarily the road stretch would be traversed at a speed of 50km/hour, determine the
running speeds Northbound and southbound in units of km/hr.
(20marks)
Table Q2
Run direction
Test vehicle
overtaking
Vehicles
overtaking test
vehicle
Vehicles in
opposing
stream
Travel
speed(km/h)
2
1
1
0
0
2
1
3
1
0
2
2
3
1
0
2
1
2
3
0
100
105
103
110
101
98
97
112
109
107
40.000
41.339
39.623
40.777
42.000
38.113
39.033
38.817
41.016
39.548
0
1
1
1
2
1
0
1
2
1
1
0
0
2
1
1
2
3
1
0
85
88
95
100
102
90
95
96
98
90
42.424
43.300
42.000
42.770
45.356
41.096
43.478
42.770
42.424
43.478
Northward
Southward
Question Three
a) A parking lot opens at 6am and closes at 10pm every day. Data collected on the parking
lot indicates that 70% of the parkers are shoppers, with an average parking duration of 4
2
hours, while the rest are commuters with an average parking duration of 14 hours.
Observation made is that 50% of parkers are turned away for lack of parking space. If
30% of those turned away are shoppers, and the rest are commuters, and if a total of 400
vehicles park daily, and given also a parking efficiency of 70%, determine the excess
demand.
(10marks)
Table Q3(b) shows data collected on a parking lot between 7.00am and 10pm. From this
data, determine the parking load.
(10marks)
Table Q3(b): Parking Accumulation
Time of
day
Number
of cars
parked
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
100
200
320
360
420
280
200
280
400
260
200
280
440
340
160
100
Question Four
It is intended to build a 2-lane road within an oil refinery along a route where the CBR of the
subgrade soil is 4%. The daily traffic (each direction), on the day of opening the road will likely
be 100 passages of 4-axle vehicles each exerting a wheel load of 4536 kg through each of the
two rear axles, 3619 kg wheel loads on the second axle and 1376 kg wheel load on the front axle;
200 passages of 3-axle vehicles with loads of 4536 kg wheel load on each of the two rear axles
and 917.5 kg wheel load on the front axle; and 100 passages of two – axle vehicles with 4077.5
kg wheel load on the rear axle and 1376 kg on the front axle. The road is required to have a 20year design life. With the aid of the provided figures design this road using the road Note 29
design methodology. (20 marks
Table Q4(a)
Traffic Loading class
Equivalent Standard Axles(x106)
T1
25-60
T2
10-25
T3
3-10
3
T4
1-3
T5
0.25-1
Table Q4(b)
Sub-grade Class
CBR (%)
S1
2-5
S2
5-10
S3
7-13
S4
10-18
S5
15-30
S6
>30
Question Five
a) A new office park is expected to be generate 1500 homebound trips in the afternoon peak
hour. Analysts expect the trips to terminate in four residential zones as provided on Table
5(a).
(9marks)
Table Q5(a)
Zone number
Travel time from
office park(min)
1
2
3
4
10
15
25
30
4
Number of trips
attracted during a
typical afternoon
peak hour
3000
2000
1800
4000
Socioeconomic
factor from office
park to zone i
1.2
0.8
1.0
1.5
b) Table 5(b) shows the data collected on Thika superhighway by JKUAT students during a
spot speed study. Determine the standard deviation for the speeds
(11marks)
Table 5(b)
Car No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
Speed Data on Thika Superhighway
Speed(mi/h)
35.1
44.0
45.8
44.3
36.3
54.0
42.1
50.1
51.8
50.8
38.3
44.6
45.2
41.1
55.1
50.2
54.3
45.4
55.2
45.7
54.1
54.0
Car No.
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
Speed(mi/h)
46.1
54.2
52.3
57.3
46.8
57.8
26.8
55.8
43.3
55.3
39.0
53.7
40.8
54.5
51.6
51.7
50.3
59.8
40.3
55.1
45.0
48.3
Car No.
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
5
Speed(mi/h)
47.8
47.1
34.8
52.4
49.1
37.1
65.0
49.5
52.2
48.4
42.8
49.5
48.6
41.2
48.0
58.0
49.0
41.8
48.3
45.9
44.7
49.5
Car No.
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
Speed(mi/h)
56.0
49.1
49.2
56.4
48.5
45.4
48.6
52.0
49.8
63.4
60.1
48.8
52.1
48.7
61.8
56.6
48.2
62.1
53.3
53.4
64.4
64.8