AVERAGE DURATION AND PERFORMANCE OF ACTUATED SIGNAL PHASES

This paper describes an approach for evaluating alternative traffic de tection designs for a signalized intersection. The models described in this paper can be used to determine the average phase duration and fr equency of phase ''max-out'' as a function of the detector loop layout , detector unit timing, traffic demand, and approach speed. Layout and timing are described by the number of detectors on each approach serv ed by the phase, detector location on each approach, detector length, and detector unit and controller time settings. The authors have used the concept of maximum allowable headway (MAH) to combine the many pos sible combinations of layout and timing variables into one representat ive quantity, which greatly simplifies the modelling process. The perf ormance models were used to examine the sensitivity of intersection pe rformance to a range of design values. In general, both phase duration and cycle length increase with higher demands or larger MAHs. Multilo op (i.e. two or more detection zones per lane) detector designs typica lly have larger MAHs than designs with one detector loop per lane. Pha se duration and cycle length also increase for very low demand levels. In terms of performance, the maximum green duration was found to have a contrary effect at higher how conditions. Larger maximum greens wer e found to reduce delays to the phase in service by reducing the proba bility of max-out but they increased delays to drivers waiting for ser vice.