The main public transportation service in Phm Penh, the capital city of Cambodia, is motorcycle taxi (motodup) that is believed to be one of the main factors contributing to traffic congestion in the city. Bus service is available from the capital city of Phm Penh to other provinces only which are very inconvenient as a public transportation service. Therefore, city bus service, which is believed to be an effective transportation service as well as a sustainable transportation planning, will play an important role in decreasing the amount of traffic congestion. Moreover, bus service is t a suitable public mode of transportation wadays since motodup is very effective though unsafe. Bus service will be planned in the future (2035) according to a study conducted by JICA in the master plan of Phm Penh's transportation planning project.