2020-21 Diploma in Traffic Engineering
Traffic Engineering (Part 1)
Assignment
The assignment covers some topics in the module of Traffic Engineering (Part 1).
It is of 100 marks in total. You are required to complete ALL of them.
(Note: The assignment is worth 40% of your total grade / marks in the module.)
Due Date: (by 9:00 pm) 20 November 2020 (Friday)
Question 1 (25 marks)
Human Characteristics
A car is travelling at 100 km/hr when the driver sees a fallen tree that requires rapid
braking to avoid collision. Find the total distance (in metres) travelled by the car
from the moment the driver first sees the fallen tree until the car stops.
Given:
An average perception-reaction time (PRT) is 0.68 second
A constant deceleration of 10 m/s2
u: initial velocity
v: final velocity
a: acceleration
x: distance travelled
[Hint: Calculate the reaction distance and braking distance.]
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Question 1 (25 marks)
Answer:
Initial speed of u = 100 km/hr = 100*1000 / 3600 m/s = (250/9) m/s
Thus, reaction distance is
= 250 / 9 * 0.68 second
= 18.9 metres
(10 marks)
And, breaking distance is
v2 – u2 = 2 a x
02 – (250/9)2 = 2 (-10 m/s2) x
Therefore,
x = (250/9)2 / 20
x = 38.6 metres
(10 marks)
Hence, total stopping distance = 18.9 + 38.6 = 57.5 metres
2
(5 marks)
Question 2 (25 marks)
The table below gives the design traffic flow at a 3-stage signalized T-junction.
There should be 1 second All Red for stages 1 and 2 as well as 3 seconds All Red for
stage 3. You may assume the turning radius to be 20m for left turn and 25 m for right
turn.
Movement
Number of
Traffic Flow
Stage
Lanes
(pcu/hr)
West Bound Straight Ahead
2
875
1
East Bound Exclusive Right Turn
1
249
2
North Bound Exclusive Left Turn
1
203
3
(a) Sketch the stage diagram for the method of signal control.
(1 mark)
(b) Determine:
(i)
Saturation flow for each movement;
(ii)
Flow factors for each movement;
(iii)
Lost Times;
(iv)
Optimum cycle time.
(14 marks)
(c) If the actual cycle time is 90 seconds, determine:
(i)
Effective green times and actual green times for each movement;
(ii)
Reserved capacity.
(10 marks)
3
Question 2 (25 marks)
(a)
1L
1L
875
2L
203
Stage 1
(WB)
Stage 2
(EB)
Stage 3
(NB)
(b)
(i)
Assumed lane width w = 3.5m for each traffic lane.
WB Traffic:
Nearside lane S = 1940 + 100 (3.5 – 3.23) = 1965 pcu
Non-nearside lane S = 2080 + 100 (3.5 – 3.25) = 2105 pcu
Total Saturation Flow = 4070 pcu/hr
EB Traffic:
Right turn lane SR = S / (1 + 1.5 / r) = 1965 / ( 1 + 1.5 / 25) = 1854 pcu/hr
Total Saturation Flow = 1854 pcu/hr
NB Traffic:
Left turn lane SR = S / ( 1 + 1.5 / r ) = 1965 / ( 1 + 1.5 / 20) = 1828 pcu/hr
Total Saturation Flow = 1828 pcu/hr
4
(ii)
WB Traffic (Stage 1):
EB Traffic (Stage 2):
NB Traffic (Stage 3):
All Stage:
(iii)
(iv)
5
(c)
(i)
WB Traffic (Stage 1):
EB Traffic (Stage 2):
NB Traffic (Stage 3):
(ii)
6
Question 3 (25 marks)
(a) What are longitudinal markings? What are transverse markings?
What is the general use of directional arrows?
(9 marks)
(b) What is the difference between these two sets of temporary traffic sign shown
below?
(4 marks)
Set A
Set B
Using the below 3 traffic signs used in Hong Kong to answer the following questions.
Sign C
Sign D
Sign E
(c) What are the Traffic Sign (TS) numbers of the signs above?
(6 marks)
(d) Which type of traffic sign does each of them belong to?
e.g. regulatory sign, warning sign or informatory sign, etc.
(6 marks)
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Question 3 (25 marks)
(a)

Longitudinal markings are placed along the direction of traffic on the roadway
surface, for the purpose of indicating to the driver, his/her proper position on
the roadway
(3 marks)

Transverse markings are marked across the direction of traffic. They are marked
at junctions etc.
(3 marks)

Directional arrows are road markings that should be used to guide the drivers in
advance over the correct lane to be taken while approaching junctions
(3 marks)
(b)

Set A: Vehicles may pass either side to reach same destination

Set B: Keep left and keep right, vehicles pass these two sides to reach different
destinations
(2 marks)
(2 marks)
(c)



Sign C: TS115 [No entry]
Sign D: TS102 [Give way]
Sign E: TS416 [Road Narrows on Right Ahead]
(2 marks)
(2 marks)
(2 marks)

Sign C: “No entry” is a regulatory sign
(2 marks)


Sign D: “Give way” is a regulatory sign
Sign E: “Road Narrows on Right Ahead” is a warning sign
(2 marks)
(2 marks)
(d)
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Question 4 (25 marks)
(a) Generally speaking, what is the difference between white road markings and the
yellow road markings?
(6 marks)
(b) What is the desirable minimum visibility distance for entry to a roundabout and
visibility distance for primary signals to a signalized junction respectively. Assuming
both speed limits are 70km/hr?
(4 marks)
(c) Determine which junction design will you use with the following conditions:
(i) low and unbalance traffic flow for a 3-arm junction;
(3 marks)
(ii) moderate traffic flow for a 4-arm junction, with heavy flow on right-turn
movement;
(3 marks)
(iii) moderate and unbalance traffic flow with requirement for better pedestrian
crossing facilities;
(3 marks)
(iv) high traffic flow and in order to minimise delay;
(3 marks)
(v) moderate and unbalance/platoon traffic flow and would like to minimize delay
for a number of junctions in an area/district;
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(3 marks)
Question 4 (25 marks)
(a) White markings – direct and control moving vehicles
Yellow markings – indicate parking and stopping restrictions
(3 marks)
(3 marks)
(b) Roundabout: 125m;
(2 marks)
Signalised junction: 120m or 125m [owing to different versions of TPDM]
(2 marks)
(c)
(i)
(ii)
(iii)
(iv)
(iii)
Priority Junction;
Roundabout;
Signalised Junction;
Grade-separated Junction;
Signalised Junction;
(3 marks)
(3 marks)
(3 marks)
(3 marks)
(3 marks)
~ END ~
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