In urban zones where bus flows are high (150 or more buses per hour in a road) in periods with significant passenger demand, bus-stops become the critical source of delay for buses, rather than junctions. In such circumstances, it is only possible to provide enough capacity by means of multiple berth bus-stops. Behaviour at this sort of facility is a complex modelling problem, with many intervening factors. A simulation program (IRENE) has been built. It allows estimation of capacity and delays at bus stops under a variety of design, operation and demand conditions. Primary versions of the program dealt with an isolated bus-stop but now it has been extended to take account of its interaction with nearby signalised junctions, in order to make it more realistic. This paper presents some major results regarding the effect on the bus-stop capacity of the existence of a downstream signalised junction. It is found that as a consequence of the presence of a signalised junction ahead the bus-stop capacity can be reduced but there is a broad reduction range (typically 0-30%). Known formulations, like the one proposed by the Highway Capacity Manual, make the decrease dependent only upon the effective green time ratio at the traffic signal. Here it is shown that this is but one of four main factors including signal cycle time, operating rules at the bus-stop and the distance from this to the stop line. The impact on bus-stop capacity of the downstream junction can be diminished, and even avoided, through an adequate design of those factors. (A)
Samenvatting