How are travel time and delay studies used? Describe one method for collecting travel time and delay data at a section of a highway. Explain how to obtain the following information from the data collected: (a) travel time, (b) operational delay, (c) stopped time delay, (d) fixed delay, and (e) travel time delay.

Question

What will be an ideal response?

Answer 1

Travel time and delay studies are used to 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. Data from these studies may be used to determine the efficiency of a route with respect to its ability to carry traffic, identify bottleneck locations with relatively high delays and the causes for those delays, perform before and after studies to evaluate the effectiveness of traffic operations improvements, determine the relative efficiency of a route by developing congestion indices, determine travel times on specific links for use in assignment models, and perform economic studies in the evaluation of traffic operation alternatives that reduce travel time. There are several methods for collecting travel time and delay data including the floating car method, the average car method, and the moving vehicle technique. In the average car method, the test car is driven 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. The time to traverse the section is noted and the test run is repeated for a minimum number of times, with the average time then being recorded as the travel time. An additional stop watch would be used to measure the amount of time the test vehicle is delayed by impedance of other traffic such as vehicles parking, or by a reduction in the capacity of the roadway such as a work zone. This value is recorded as the operational delay. During the test runs, the amount of time the vehicle is stopped would also be recorded and the average from all runs would be recorded as the stopped-time delay. The fixed delay would be measured as the time spent waiting for a traffic signal along the route to turn green. This delay is independent of other traffic. The travel time delay would be determined by subtracting the travel time for a vehicle to traverse the study section under uncongested conditions from the actual travel time.