Abstract
Highway Capacity Manual (HCM) of USA provides techniques for evaluation of capacity and quality of service of any facility. Studies have shown that these techniques have limited application for heterogeneous traffic situation prevailing in the developing world. As motorcycles are found in large numbers on the urban roads of developing countries; the present study tries to determine their effect of on the capacity of four lane urban roads.
The study was carried out in Songkhla province of Thailand, where speed-volume relationship was used for capacity estimation. It was found that similar to the study carried out in India, the capacity of four lane urban roads in Thailand increases with the increase in percentage of motorcycle in the traffic stream. However, though the estimate of capacity was very close to that recommended by the Indonesian highway capacity manual, it was different from the estimated values for similar traffic situation in India.
