Saturation flow versus green time at two‐stage signal controlled intersections
Intersections are the key components of road networks considerably aff ecting capacity. As fl ow levels and experience have increased over the years, methods and means have been developed to cope with growing demand for traffi c at road junctions. Among various traffi c control devices and techniques developed to cope with confl icting movements, traffi c signals create artifi cial gaps to accommodate the impeded traffi c streams. Th e majority of parameters that govern signalised intersection
... lised intersection control and operations such as a degree of saturation, delays, queue lengths, the level of service etc. are very sensitive to saturation fl ow. Th erefore, it is essential to reliably evaluate saturation fl ow for correctly setting traffi c signals to avoid unnecessary delays and confl icts. Generally, almost all guidelines support the constancy of saturation fl ow irrespective of green time duration. Th is paper presents the results of fi eld studies carried out to enable the performance of signalised intersections to be compared at diff erent green time durations. It was found that saturation fl ow decreased slightly with growing green time. Reduction corresponded to between 2 and 5 pcus/gh per second of green time. However, the analyses of the discharge rate during the successive time intervals of 6-seconds showed a substantial reduction of 10% to 13% in saturation fl ow levels aft er 36 seconds of green time compared to those relating to 6-36 seconds range. No reduction in saturation fl ow levels was detected at the sites where only green periods of 44 seconds or less were implemented.