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2019 T1 Final
Fundamentals of Traffic Engineering (University of New South Wales)
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UNSW Sydney
TRIMESTER 1 2019 EXAMINATIONS
CVEN4404: FUNDAMENTALS OF TRAFFIC ENGINEERING
1. TIME ALLOWED – 2 hours
2. READING TIME – 10 minutes
3. THIS EXAMINATION PAPER HAS 20 PAGES
4. TOTAL NUMBER OF QUESTIONS – 5
5. TOTAL MARKS AVAILABLE – 100
6. MARKS AVAILABLE FOR EACH QUESTION ARE SHOWN IN THE EXAMINATION
PAPER
7. ALL ANSWERS MUST BE WRITTEN IN INK. EXCEPT WHERE THEY ARE
EXPRESSLY REQUIRED, PENCILS MAY BE USED ONLY FOR DRAWING, SKETCHING
OR GRAPHICAL WORK
8. THIS PAPER MAY NOT BE RETAINED BY CANDIDATE
9. CANDIDATES MAY BRING TO THE EXAMINATION: UNSW approved calculator,
drawing tools (ruler, compass, protractor, Set Square) and all notes deemed
necessary to complete the exam (Open Book).
10. ANSWERS MUST BE WRITTEN IN THE SPACE PROVIDED. ONLY THE PINK
SHEETS WILL BE MARKED.
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Question 1: Traffic Flow Theory Fundamentals (20 marks)
a) The following 15 minute counts were observed during the peak hour. What is the
peak hour factor (PHF)?
Table 1: Time frame and number of vehicles
Time Frame Number of Vehicles
7:30 – 7:45 am 456
7:45 – 8:00 am 470
8:00 – 8:15 am 495
8:15 – 8:30 am 451
(3 marks)
b) The following speeds (in km/hr) were observed for 5 vehicles on the Hume Highway
(Northbound).
58.9, 62.5, 71.3, 77.6, 74.5
What is the time mean speed?
(2 marks)
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c) For the data in part b) what is the space mean speed?
(2 marks)
d) If the standard deviation of speeds on the Hume Highway is estimated to be 8 km/hr,
Has the traffic engineer collected enough speed data if it is necessary to estimate the
time mean speed to within 5km/hr with a 95% level of confidence (𝑧𝑎/2 =1.96)?
How many more observations are necessary to achieve and adequate sample size?
(3 marks)
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The speed (𝑣𝑠 ) - flow (𝑞) relationship for one lane of a local road is believed to be
𝒒 = 𝟐𝟕𝟑𝒗𝒔 − 𝟕𝟎𝒗𝒔 (𝐥𝐧 𝒗𝒔 )
The speed (𝑣𝑠 ) is measured in km/hr and the flow (𝑞) is measured in vehicles/hr, given this
information answer the following questions;
e) What is the value of the free flow speed?
(3 marks)
𝑑
f) What is the speed at the maximum flow rate? (N.B. 𝑑𝑥 (𝑥 ln 𝑥) = ln 𝑥 + 1
(3 marks)
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g) What is the maximum flow rate?
(2 marks)
h) What is the density at the maximum flow rate?
(2 marks)
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Spare sheet for extra working out for Question 1
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Question 2: Shock wave theory (20 marks)
a) Briefly describe any 4 different shock waves that can form within a traffic stream and
the associated traffic conditions that will result in each of these shock waves. (4)
b) Traffic surveys have indicated that the traffic flow behaviour on a two-lane two-way
highway can be described by the Greenshields model. Nearby commercial and
residential developments need additional underground electrical and
telecommunications cabling. This requires roadworks to be completed along a 0.8km
length of the shoulder of the highway (see Figure 1).
As a safety measure, a “work zone” is put in place which operates for a period of
2hrs. The posted speed limit for the work zone during its operation is 30 km/h. Data
collected at the site under normal traffic conditions show that the jam density and
mean free flow speed for each lane are 125 veh/km and 90 km/h respectively. If the
flow present on the highway at the time of operation of the work zone is 90% of the
capacity of the highway, determine:
i. The capacity of the highway. (2)
ii. The flow present on the highway at time of operation of the work zone. (2)
iii. The speed of the shock wave created by the presence of the roadworks. (6)
iv. The number of vehicles affected by the work zone during the 2-hour operation (6)
Figure 1: Proposed roadworks for Question 2
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Question 3: Ramp Capacity and Level of Service (20 marks)
a) What is the level of service for the ramp combination and traffic conditions shown in
Figure 2? The PHF is 0.92. The terrain is level. Free-flow speed on the freeway is
100km/hr and free flow speed on the ramps is 60km/hr. All other necessary
information is presented in Figure 2. (16)
b) Can weaving occur in this configuration? If so what type of weaving would occur?
What are the two geometric parameters that describe the area used by weaving
vehicles? (4)
Figure 2: Ramp configuration for Question 3
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Question 4: Signalised Intersection LOS (30 marks)
Figure 3 presents the intersection of Bernera Road/Wroxham Street/Bomadery Drive,
located in Prestons, NSW. Table 2 provides details regarding the traffic flow and signals
structure (fixed time signals) of each of the approach to the intersection.
a) Determine the LOS for each lane group of the western approach (Wroxham Street) of
the intersection. Assume it is an isolated intersection, the traffic flow accounts for the
peak 15-minute period and that there is no initial queue at the start of the analysis
period.
(16 marks)
b) Determine the LOS of the western approach of the intersection
(6 marks)
c) Is the performance satisfactory? If not describe what options does a traffic engineer
have to improve the performance of the approach to the intersection? Briefly describe
any additional calculations the engineer would need to make to further investigate
these options?
(8 marks)
Figure 3: Intersection configuration of Bernera Road/Wroxham Street/Bomaderry Drive,
Prestons, NSW
Table 2: Traffic flow and signal timing characteristics
Cycle Time = 120 seconds
Analysis Saturation
Green
Appraoch Lane Grouping Flow Rate Flow Rate
Time (s)
(veh/hr) (veh/hr)
Left and Through 60 850 1800
Bernera Road (N)
Right 15 320 1600
Left and Through 30 350 1600
Bomaderry Drive
Right 15 130 1400
Left and Through 60 720 2000
Bernera Road (S)
Right 15 300 1800
Left and Through 30 380 2000
Wroxham Street
Right 15 120 1600
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Question 5: Gap Acceptance (10 marks)
Table 3 gives data on accepted and rejected gaps of vehicles on the minor road of a priority-
controlled intersection.
Table 3: Accepted and rejected gaps
Gap (t) s Number of Number of
Rejected Accepted
Gaps > 𝑡𝑐 Gaps < 𝑡𝑐
1.5 92 3
2.5 52 18
3.5 30 35
4.5 10 62
5.5 2 100
If the arrival of the vehicles on the major road can be described by the Poisson distribution,
and the peak hour volume is 1100 veh/hr, determine the expected number of accepted gaps
that will be available for minor road vehicles during the peak hour. (10)
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