EFFECT OF SHOULDER CONDITION ON SPEED-VOLUME RELATIONSHIP

Abstract

The shoulder is the portion of the roadway continuous with the travelled way for accommodation of stopped vehicles, emergency use and lateral support of the base and surface course. They are vital for single and two lane roads. According to available data, 15 per cent length of National Highway (NH) and 80 per cent of the State Highway (SH) are still single-lane road carrying 35-40 per cent of the total road traffic. Highway shoulders influence greatly the safety, strength and traffic carrying capacity of adjacent traffic lane. Data collected at different sections of highway with varying condition of shoulders have been analysed to determine the effect of shoulder condition on speed and placement of vehicles. Shoulders have been classified into 5 categories as excellent, good, fair, poor and worst based on their physical condition and riding quality. The analysis of data indicated that effective use of pavement gets reduced as the shoulder condition deteriorates. Also, speed of movement during crossing another vehicle reduces by 4 per cent to 33.5 per cent as the condition of shoulder changes from excellent to worst. It also depends upon width of carriageway, its condition and type of vehicle involved in crossing and overtaking manoeuvres. The speed-volume relationships drawn at different sections show that mean free speed on a section change with the condition of shoulder.