EFFECT OF BUS STOP ON CAPACITY OF URBAN ARTERIAL ROAD

Abstract

Bus stops are the designated places where passengers alight and board a public transport bus. l)iflerent types of bus stops like curbside stops, bus bays, queue jumpers, nubs, etc. are present in many cities across the world. However, only curbside stops and bus bays are predominantly present on Indian urban roads. Previous studies indicate that the presence of a bus stop ominously reduces the stream speed and capacity of an urban road. Curbside bus stops are provided on urban roads in situations where sufficient land is not available to construct the bus bays. When a bus arrives in the curbside bus stop, it obstructs movement of vehicles in the curhlane and thus reduces the capacity of the road. On the other hand, bus bays create problems to bus drivers during i-c-entering the traffic stream. 1'rallic data were collected from several 6-lane and 4-lane divided arterial road sections in New l)elhi. The data collection included few sections without any side friction (to estimate base capacity). sections with curbside stops and also a section with bus bay. To determine the capacity reduction due to curbside stops on both 4-lane and 6-lane roads, three methods are used in this study. In the first method, capacity values are estimated for each section based on speed-flow diagrams and then the capacity of the base sections are compared with that of sections with bus stop. This method is based on empirical data and reduction factor could not he related with bus frequency or traffic volume. Secondly, an empirical formula based on lane changes is proposed in this study to determine the capacity reduction factor. Graphs are plotted relating lorced Lane Changes and traffic volume with capacity reduction factor. The third method is based on the bus frequency and 5-minute traffic flow rate on the road. The developed methods are validated by collecting traffic data at other road sections on 4-lane and 6-lane roads. All the three methods are found to give consistent results. but the third method is recommended for practising engineers as it requires simple data on bus frequency and traffic flov rate. l)ue to loose structure of regulatory system and poor lane discipline on Indian roads, buses many a times, do not stop at their intended stops. Two sections of six-lane arterial roads with curbside bus stops are analyzed to observe the impact of the stopped bus on number of lane changes, stream speed and capacity of the midblock section. It was observed that in majority of the cases the buses did not stop in their designated area. and several reasons are idcntilied from the videos for this behaviour. These include bus bunching, stopped vehicles in the curb lane or passengers standing in the area marked for the bus. All these reasons force the driver to if stop the bus outside the marked area. In order to quantify this untidy stopping of buses, a new parameter called effective stopped position of buses (E01,) is introduced in this study which is determined from the position of the bus and the dwell time. Forced lane changes, stream speed and reduction in the capacity are found related to effective stopped position of buses observed in a count period of 5 minutes. It is shown that capacity of the midblock section of a six-lane divided road reduces by 11.2 percent f or a dwell time of 40 s when effective position of all buses stopping in 5 mm is more than 5 m. 13us bays are normally constructed on urban roads to reduce the delays to through traffic when number of stopping buses are very high. They are expensive to construct and also require more space for construction than any other type of bus stop. Firstly, the influence length of the bus hay is estimated using GPS based V-Box device by employing chase bus method. Then the a capacity drop of a 4-lane arterial section due to bus bay is estimated from speed-flow plots.