Date of this Version
Journal of Transportation Engineering (July 2007) 133(7): 415-422. DOI: 10.1061/(ASCE)0733-947X(2007)133:7(415).
The Highway Capacity Manual uses the arrival type (AT) as a mechanism to account for the quality of traffic signal coordination in the calculation of delay at a signalized intersection. Although there is much discussion in the literature regarding the accuracy and precision of this approach, the AT parameter provides a simple mechanism for grading the performance of traffic signal coordination. This paper describes data collection limitations of current traffic signal controllers and proposes a procedure where the AT parameter can be calculated by traffic signal controllers in real time. Given that the nation received a score of 61 out of a possible 100 points for coordinated systems on the National Traffic Signal Report Card, this method is particularly timely as it provides an easily obtainable quantitative measure of traffic signal coordination. Data from a coordinated system in Noblesville, Ind., is analyzed and presented in a format that can be used to assess arterial performance. Results from the test site show that the quality of progression of the northbound approach was “favorable” to “highly favorable” during the p.m. coordinated period (peak direction) and “random” to “favorable” during the a.m. coordinated period (off-peak direction). As expected, the quality of progression for the northbound approach during noncoordinated periods and the southbound approach (which is approximately 1.6 km from the nearest upstream signal) during all periods was generally found to be “random.”