Citation

Teply S. Transp. Res. Rec. 1993; 1398: 101-110.

Copyright

(Copyright © 1993, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

unavailable

PMID

unavailable

Abstract

Quality of service at transportation facilities can be determined from a number of objectively measurable criteria. For signalized intersections, delay has been accepted internationally as the prime measure of performance and, in the United States, as the sole basis for the level-of-service measures. In other countries, several other parameters or their combinations are also used, usually as additional measures related to specific design or evaluation objectives. A pilot project at the University of Alberta, which investigated the potential of a supplementary criterion--the probability of discharge overload--is the basis of the discussion. This measure would indicate in how many cycles the number of vehicles left over from the previous cycle plus the number of vehicles arriving exceeds capacity. Such information would assist in the analysis of a specific lane problem. Vehicle demand in successive cycles is treated as a series of dependent events on the basis of the Poisson distribution of arrivals. Surveys and simulations of an overload factor, which somewhat extends the concept of the load factor used in the 1965 Highway Capacity Manual, are used as indications of which probability type would provide the most practical representation of measurable parameters. The results of the pilot project suggest that the probability of an overload in one, two, or both of two consecutive cycles is a strong candidate to approximate the percentage of cycles with discharge overloads. It is mathematically simple and, because it resembles the overload factor, easy to measure.

Record URL:
http://onlinepubs.trb.org/Onlinepubs/trr/1993/1398/1398-014.pdf

Language: en

Keywords

Mathematical models; Traffic control; Traffic signals; Quality assurance; Performance; Probability