The capacity of a priority controlled intersection depends on the availability of acceptable gaps in the conflicting traffic stream. Current methods of predicting capacity are often based on the assumption that conflicting vehicles arrive randomly, or at best allow for a minimum headway. Due to restricted overtaking opportunities, as well as the impact of traffic signals, platoons are formed in the traffic stream. Headways in the traffic stream can therefore be categorised into large inter-platoon gaps and a concentration of vehicles in closely spaced platoons. Current methods therefore seriously underestimate the number of acceptable gaps when such platooning occurs. The effect of platooning on capacity is nearly as on capacity is nearly as important as the effect of the opposing traffic volume itself. Possible errors are of sufficient significance to warrant the inclusion of the effect of platooning in capacity calculations. A relatively simple modification to Tanner's capacity model is proposed to account for this phenomenon. Consideration should be given to this aspect for possible future inclusion in the Highway Capacity Manual (HCM). (A)
Samenvatting