TRAVEL TIME AND DELAY STUDIES
• A travel time study determines the
amount of time required to travel from
one point to another on a given route. In
conducting such a study, information
may also be collected on the locations,
durations, and causes of delays.
TRAVEL TIME AND DELAY STUDIES
When this is done, the study is known as a travel
time and delay study. Data obtained from travel
time and delay studies give a good indication of
the level of service on the study section. These data
also aid the traffic engineer in identifying problem
locations, which may require special attention in
order to improve the overall flow of traffic on the
route.
Applications of Travel Time and Delay
Data
The data obtained from travel time and delay studies
may be used in any one of the following traffic
engineering tasks:
• Determination of the efficiency of a route with
respect to its ability to carry traffic.
• Identification of locations with relatively high
delays and the causes for those delays
• Performance of before-and-after studies to evaluate
the effectiveness of traffic operation improvements
Determination of relative efficiency of a route by
developing sufficiency ratings or congestion indices.
Determination of travel times on specific links for use
in trip assignment models.
Compilation of travel time data that may be used in
trend studies to evaluate the changes in efficiency and
level of service with time
Performance of economic studies in the evaluation of
traffic operation alternatives that reduce travel time.
Definition of Terms Related to Time
and Delay Studies
1. Travel time is the time taken by a vehicle to traverse a
given section of a highway.
2. Running time is the time a vehicle is actually in motion
while traversing a given section of a highway.
3. Delay is the time lost by a vehicle due to causes beyond
the control of the driver.
4. Operational delay is that part of the delay caused by
the impedance of other traffic. This impedance can occur
either as side friction, where the stream flow is interfered
with by other traffic, or as internal friction, where the
interference is within the traffic stream (.
5. Stopped-time delay is that part of the delay during
which the vehicle is at rest.
6. Fixed delay is that part of the delay caused by control
devices such as traffic signals. This delay occurs
regardless of the traffic volume or the impedance that
may exist.
7. Travel-time delay is the difference between the actual
travel time and the travel time that will be obtained by
assuming that a vehicle traverses the study section at an
average speed equal to that for an uncongested traffic
flow on the section being studied.
There can be different forms of delay
depending on location:
• Stoped time delay - It is the delay during
which the vehicles is at rest
•Approach delay - It is due to deceleration
to and acceleration from a stop to stopped
time delay.
• Time-in-queue delay - It is the time between a
vehicle joining the end of the queue at a signalized or
stop-controlled intersection and the tie it crosses the
intersection (stop line).
• Control delay (or fixed delay) - It is the delay caused
by controlled device such as signals, includes both
approach delay and time-in-queue delay.
• Operational delay - It is the delay caused due to
impedance of other traffic.
There are several methods to conduct travel time
and delay studies, namely:
Those using a test vehicle
• Floating car technique - In this method, the test
car is driven by an observer along the test section
so that the test car “floats” with the traffic.The
driver of the test vehicle attempts to pass as many
vehicles as those that pass his test vehicle. The time
taken to traverse the study section is recorded.
Average speed technique - This technique
involves driving the test car along the length of
the test section at a speed that, in the opinion of
the driver, is the average speed of the traffic
stream.
Example: Determine the congestion delay for a road
section 335 m length with average running speed of
21 Km /hr based on : a- speed limit 50Km/hr ,and
average spot speed b- 26.9Km/hr.
Solution:
Running time at running speed = ( 335m /21) =
57sec
A- Based on limit speed. (335/50) = 24 sec
Congestion delay = 57 - 24 = 33sec.
b- Based on average spot speed (335/26.9)= 44.8 sec
Congestion delay = 57 - 44.8 = 12.2sec.
• Moving vehicle technique - In this technique, the
observer makes a round trip on a test section like
the one shown in Figure 3
Those not requiring a test vehicle.
License plate observations.
Interview.
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