途上国における都市鉄道のフィーダーシステムとしてのパラトランジットに関する研究 : バンコクを対象として

In many megacities of developing countries, at present, several plans of mass transit network expansion linking with suburban areas are under process; however, to provide excessive network is financially infeasible. This has resulted in difficulty of accessing mass transit stations – one of mass transit planning issues – especially in short to intermediate distances from the stations. To solve this problem, it might not be effective to directly apply approaches experienced by developed countries because of differences in characteristics of cities between the developing countries and the developed countries especially urban structures and people preferences. Poor road network and land use development in urban areas of developing cities caused difficulties in providing adequate public transport services. Moreover, transitional economies and development of megacities of developing countries inevitably differ greatly in economic, demographic characteristics and income that have induced varieties of people. These variations brought about various needs of commuting and perceptions and attitudes towards transport modes. According to the growth of motorization and public transit deficiency, people in urban areas are discouraged to use public transport. Private vehicles - car and motorcycle - have become preferable modes to those who can afford, notwithstanding the fact that mass transits have been implemented. It is because private car offers convenience and door-todoor function which have been considered much advantageous over mass transit and public transport. Currently, paratransit emerges as one of transportation modes and gradually becomes an outperforming mode in connecting people between their residences and public transport specifically in areas left by public transport. Paratransit continues its dominant function as a feeder in several megacities of the developing countries due to their services satisfying captive riders in terms of mobility and door-to-door services. It is because of the advantages of vehicle size and unrestrained operation that make paratransit response to fluctuating demand. In addition, a combination of paratransit as a feeder and public transports becomes one of typical travel choices for commuters and this will continue into the future. In recent years, studies regarding paratransit in developing countries have become popular. Most studies mainly concerned with paratransit itself such as service characteristics and position in transportation hierarchy (Cervero, 1998; Cervero, 2000; Regidor, 1999; Shimazaki and Rahman, 1996); and market structures, regulations and impacts of paratransit on transportation system (Cervero and Golub, 2007; Diaz and Cal, 2005; Leopairojna and Hanaoka, 2005). Paratransit’s feeder potential and performance in urban transportation have gradually been examined (Loo, 2007; Okada et al., 2003; Satiennam et al., 2006). Public perception was recognized as an important tool in evaluating paratransit operation and its future (Joewono and Kubota, 2006). The previous researches could provide valuable information, insight of paratransit performance and the ability for integrating paratransit as a feeder into mass transit system, with anticipation, to improve the performance of the existing transport modes that seem more financially and economically feasible for the developing countries. Paratransit, nevertheless, often experiences malignity because its informal services lead to traffic congestion, safety threats and pessimistic images. Consequently, it has been ignored by transportation planners and policy makers and study regarding this integration has not been performed. Therefore, this research aims to render and provide one of the important steps to achieve the policy for enhancing public transport performance and urban transportation in developing countries through the idea of integrating paratransit as a feeder into mass transit system. As the distances connecting between mass transit station and commuter’s origins and destinations are too short to offset total travel delays and paratransit services in developing countries are considered informal, this research, therefore, focuses mainly on commuter perceptions of paratransit services and trips accessing mass transit stations that will be important keys for future development of integrating paratransit as a feeder. Since access is the starting point of the mass transit and public transport trips, it is, therefore, vital to understand influences of paratransit service on commuters’ perception and attitudes to their trips accessing mass transit station and willingness to use paratransit and mass transits in order to promote paratransit as a feeder. Besides, assuming simplicity of people’s homogeneity in developing countries, typically applied in most transportation studies, might obtain misleading outcome due to large divergences of commuters’ statuses and needs. Thus, this research proposed to provide basic framework and a beginning step of managing the existing paratransit and future planning of access development around mass transit stations. In addition, this research aims to investigate several influences of commuters’ perceptions and attitudes to paratransit services on the trip accessing mass transit stations and willingness to use mass transit and paratransit as feeder mode, and to emphasize the importance of considering effects of commuter heterogeneity in the transportation planning of the developing countries. This research was carried out using study areas along mass transit corridors in Bangkok, Thailand, where large income differences were appearing, vehicle ownership was increasing, several plans of mass transit were arranging, and varieties of paratransit were functioning as a feeder. Demand-based paratransit, motorcycle-taxi, and route-based paratransit, Songtaew, were selected to be investigated. Though pessimistic attitudes to inconvenience and difficulties of using a travel choice of combination between paratransit and public transport, especially risks in terms of safety and security, dissatisfied and discouraged commuters to use this travel alternative, paratransit services were still taken into consideration by the commuters. Flexible and door-to-door services offered by the motorcycle-taxi and safety and security of paratransit operation showed positive influence on satisfaction of trip accessing mass transit stations that encouraged commuters to use mass transit and paratransit in the future. In addition, inevitable outcome was found while heterogeneity of people was considered. Low income commuters assessed their satisfaction of access trips mainly on out-of-pocket expenses while commuters in higher status mainly awarded on access time. Motorcycle-taxi positively influenced the high income; however, its safety and security posed negative impacts to all commuters. Songtaew, in contrast, was a favorable mode of the low income, because it offered cheaper and safer services; nevertheless, commuters suffered its unreliable waiting and travel time. Both demand-based and route-based paratransit had their own service areas, potential users, and different influences on various types of commuters. These findings would provide effective ways of planning of integrating paratransit as a feeder into mass transit systems. Based on these attempts, this research highlights advantages and future potential of paratransit in urban transportation, and emphasizes seriousness of heterogeneity of commuters for enhancing effectiveness of transportation planning and development in developing countries.横浜国立大学, 平成22年9月30日, 博士（工学）, 甲第1315