Environmental Capacity of Roads Under Mixed Traffic Conditions

Abstract

Transportation provides basic mobility and accessibility for people and goods between different origins and destinations. However, this benefit costs us congestion and deteriorated environmental quality. In recent years, road transport has been one of the major contributors of pollutants like hydrocarbons, carbon monoxide, particulate matter, etc. In transport infrastructure planning, one important aspect is determining the need and capacity of roads. Several researches, in this aspect, so far considered different traffic flow theories to estimate the maximum number of vehicles that can be accommodated under certain traffic conditions. However, these researches neglect the impact of traffic on the environment in estimating capacity. Thus, amalgamated research on traffic and the environment is the need of the hour. This research aims to develop a methodology for determining the environmental capacity of roads from three perspectives, namely: road capacity restraints, air pollution restraint, and noise pollution restraint conditions. The environmental capacity, considering the above three conditions, is estimated in the range of 60–70% of its capacity for eight- and six-lane divided roads and approximately 50% for four-lane divided and two-lane undivided roads. Further, a correction factor is derived for four different boundary conditions by carrying out dispersion modelling. The correction factor is estimated to be 0.93 for one-side built up, 1.09 for street canyon and 0.72 for open terrain with respect to both sides built-up boundary conditions. Thus, overall, this research could provide a theoretical and reliable database for traffic optimization, air and noise pollution control, i.e. conducive to transport as well as environmental planning and management.