Abstract
The Highway Capacity Manual (2000) states that the capacity of a 2-lane rural highway under ideal conditions is 3200 passenger car units/hr for both directions combined. The ideal conditions as given in the manual do not include the riding quality of a road, which deteriorates with time. This paper shows that the capacity of a 2-lane rural road is also affected by the road roughness. Data collected on the roughness and free-flow speed of cars and heavy vehicles at a length of 55 km on 3 highways in India was used to establish the relationship between these 2 variables. Further, speed-volume data collected at 8 different sections of 2-lane roads were analyzed and the effect of road roughness on capacity was evaluated.