Operational Performance Measures for Two-lane Roads: An Assessment of Methodological Alternatives☆

Two-lane roads represent the majority of the highway system in India. The analysis of traffic performance on two-lane roads is critical for their planning, design, maintenance, rehabilitation, and operation. It is a major input to important decisions on public fund investments that are made at different stages of the highway life. Performance evaluation is typically carried out with the capacity analysis for various highway facilities. Many countries in the world have a standard methodology for capacity analysis procedure. In general, performance of a highway is expressed in terms of level of service (LOS), which is a scheme intended to depict traffic conditions for an existing or proposed transportation facility operating under current or projected traffic demand. Evaluating the performance of the two-lane roads is not an easy task because of several distinct characteristics associated with these roads. IRC: 64-1990 provides some guidelines for capacity of two-lane roads; however, these guidelines provide very little information on LOS and its evaluation on these roads. As a result of that planners in India use the methodologies given in the Highway Capacity Manuals (HCM) of other developed countries. But these methodologies may not be applicable for Indian mixed traffic condition. This adoptation can cause serious consequences in situations where capacity augmentation by widening of the roads will cost huge amount of money. Therefore, it is necessary to examine the concerns expressed above and evaluate operational performance measure(s) used by researchers across the globe which would be appropriate and applicable to Indian conditions. This paper summarises the evolution of research on determining the LOS of two-lane roads and provides a discussion for future directions pertinent to Indian mixed traffic situation.