IMPACT OF MOTORCYCLES AND SHOULDER WIDTH ON TWO-LANE HIGHWAY CAPACITY IN THAILAND USING TRAFFIC MICRO-SIMULATION MODEL

The effect of motorcycle and shoulder width on two-lane highway capacity using a traffic micro-simulation model was investigated, together with other effect factors, which are heavy vehicles and access points. Four sections of a two-lane highway that have different shoulder widths were selected for the study. Under prevailing conditions, a two-lane highway with a shoulder width of fewer than 1.5 meters will cause a motorcycle to interfere with the carriageway and other impact factors that make capacity significantly less than HCM2010 calculation. The analysis of the base conditions model determined that the maximum capacity of a two-lane highway with a shoulder width of 2.0 meters was 1979 passenger car/hour/direction. Two-lane highways with shoulder widths of 1.5, 1.0 and 0.5 meters recorded maximum capacity at 1914, 1860 and 1789 passenger car/hour/direction, respectively, with all results higher than the HCM 2010 calculation. Model equations for capacity estimation were developed using multiple linear regression analysis derived from the relationships between capacity, shoulder width, and other affecting factors. Results can be used as guidelines for the future capacity assessment of two-lane highways in Thailand.