Speed based capacity model for urban arterial roads

摘要

Capacity of an urban road is influenced by several geometric, environmental and traffic factors. It is also influenced by side friction factors like walking and crossing of pedestrians, presence of bus stop and number of non motorized vehicles present during field observations. Highway capacity manuals in different countries consider the influence of all these factors in estimation of urban road capacity. However, the effect of city size and pavement condition is generally ignored. Driving behavior and operating speed (OS) on urban arterial is greatly influenced by the road condition and size of the city. Therefore, it will be worthwhile to explore the relation between OS and capacity of an urban arterial road. Field data of speed and traffic volume are collected on different sections of six-lane and four-lane urban arterial roads in four different cities of India. Free slow speed (FFS) of car is also measured in the field and operating sped is taken as 85th percentile of FFS data. OS is found highest in New Delhi which is the most populous city whereas the least in Chandigarh which is less populous. Capacity of all the sections was estimated by plotting the speed-flow diagram. A statistically significant relation is presented between capacity of urban road and its operating speed. The model may be used for quick estimation of capacity at any section of urban arterial roads.