SPEED-FLOW CHARACTERISTICS OF INTERMEDIATE LANE ROADS

Abstract

Intermediate lane roads constitute major proportion of road network of the state highways, major district roads, other district roads and rural roads and some proportion of national highways. These roads due to reduced width of pavement and complex traffic composition have lesser operating speed and capacity than the two lane roads. Also, the speed-flow characteristics on intermediate lane roads vary significantly from two-lane roads, necessitating seperate consideration. The concept of intermediate lane roads is not common in developed countries and their studies are limited to two lane roads and models developed on two lane roads are not applicable to intermediate lane roads, because of restricted width of pavement. In present study, an attempt has been made to study the effect of shoulders and traffic composition on speed flow characteristics and hence capacity of intermediate lane roads. The data collected at seven sections in three states namely Uttarakhand, Gujarat and Kerala have been analysed and speed-flow relationships are drawn. Also, the effect of shoulder width and proportion of each vehicle type on capacity is determined. Results indicate that the capacity of an intermediate lane road is around 2050 PCUs/hr which is more than the suggested capacity value of 1500 PCUs/hr by IRC: 64-1990. It increases with increase in shoulder width and percentage of 2W in traffic composition, whereas decreases with increase in proportion of other types of vehicles. The results of this study will be very useful in revising the IRC guidelines. iii