Evaluation of Rate of the Reduction in Road Capacity at Kerb side Bus Stop in Urban areas under Mixed Traffic conditions – a case study in Hyderabad city

Abstract

Capacity of mid block, in general represents the maximum hourly rate at which vehicles reasonably can be expected to traverse a point or section of a lane during a given time period under prevailing roadway and traffic conditions. Roadway conditions refer to the type of facility, its geometric characteristics, the number of lanes, lateral clearances, design speed, horizontal and vertical alignments. Traffic conditions refer to the composition and distribution of traffic in available lanes. Improvements and changes in geometric features, junction features, traffic control devices and traffic management measures can be designed effectively by proper estimation of capacity. The adequacy or deficiency of a network can be assessed by comparing the present traffic volume with the capacity of existing network. The distribution of traffic in each lane can be planned by measuring its link capacity. The capacity of mid block is not only a function of available road width but varies based on the traffic volume and its composition and other impedances that act on traffic flow continuously. In a mixed urban traffic flow, when the flow rates approaches to capacity, the congestion takes place causing excessive delay to vehicles. In the present study, three kerb side bus stops in Hyderabad city of varying road widths and traffic characteristics are considered to evaluate the reduction in roadway capacity due to kerb side bus stop under variable roadway and traffic conditions. Whenever a bus, stops at a kerb side bus stop, the effective road width available for traffic movement reduces there by creating a bottleneck situation. The impedance caused by the activity of buses at a kerb side bus stop on the quality of traffic can also be assessed by comparing the capacities of the road not affected by the bus stop and the bottleneck or the capacity resulting due to reduced road width. An attempt is made in this study to understand the reduction of capacity at each of the selected bus stops. Using curve enveloping technique, capacity graphs are plotted based on speed – volume relationships for the sections of road, away from the bus stop and also at the bus stop. A comparison of these graphs indicates the reduction in capacity due to the kerb side bus stop. This reduced capacity is a key factor that influences the traffic dynamics at the bus stop and the complex relationships between the various parameters that are inherently affected by these capacity values.