Vehicle Composition and Lane Distribution in Multilane Highways in Indonesian Cities

Recently, vehicle composition in Indonesia was changing drastically. Worsening congestion, forced some travellers from all income levels to choose motorcycle and therefore motorcycle prercentage in vehicle composition became higher than default values in Indonesian Highway Capacity Manual (IHCM) 1997 as found in Jakarta, Bandung, Surabaya and Mataram. In IHCM (1997) default values, the larger the city, the lower the motorcycle percentage in traffic. Recently, such pattern was no longer exist. At present paper, additional observation results in Medan and Makassar will be compared with the previous research. Change in vehicle composition will change the distribution of different types of vehicles accross lanes in multilane highways. Observations were made in four lanes-two ways and six lanes-two ways divided highways. It was in general found that in 24 hours observation, most light vehicles and heavy vehicles were using the median lane or middle lane, whilst most motorcycles were using the curb lane or middle lane.