Influence of vehicle size and performance on intersection saturation flow

Data were collected on 15138 vehicles discharging from a signalized intersection when there were always more vehicles waiting to pass through than the green phase would permit. Saturation flow was examined as a function of vehicle length and headway. Vehicle size was also characterized by number of axles. The performance of the lead vehicle for each cycle was characterized by the time it took, after starting from a stop, to clear the intersection. It is concluded that: 1) smaller cars give higher intersection saturation flow; 2) when a queue leader is a low performance vehicle, saturation flow is reduced. One vehicle per cycle is lost for each additional two seconds the lead vehicle takes to clear the intersection; 3) vehicles with low performance reduce saturation flow; 4) large trucks are over-represented in queue leader positions; 5) automatic traffic control schemes to minimize total system fuel use should strive to reduce likelihood of large trucks being queue leaders; and 6) the fraction of large trucks in the sample observed to "run the red" was larger than the corresponding fraction for passenger cars. For the covering abstract of the symposium see TRIS 452544. (TRRL)