| Summary: | 碩士 === 國立臺灣大學 === 土木工程學研究所 === 89 === Public transit system has three important factors：subsidy, fare, service of level. This research focuses on the study of financially sustainable subsidy mechanism for public transit system. This study used analysis optimization approach to formulate the mathematical function. The model considers maximum social welfare objective with break-even constraints of route to conform with financially sustainable objection. This study considers three types of subsidy funds and analyzes their distinct effects on public transit system. Three subsidy financial resources include：government expenditure, car tax expenditure, and bus tax expenditure. The car tax expenditure model replies an extra-subsidy while the bus tax expenditure model intra-subsidy.
The results indicate that the government expenditure and extra-subsidy cause the lower bus fare and the shorter bus route headway but intra-subsidy causes the higher bus fare, the shorter headway of bus route under subsidy and the higher headway of bus route under non-subsidy. Furthermore, if the bus route length shortens or average trip length of bus route under subsidy increases, the government must raise the amount of subsidy in order to maintain the same bus service level. If the bus average speed raises, average trip length of bus route under non-subsidy increases or the ratio between waiting time and headway decreases, the government can reduce the amount of subsidy money in order to maintain the same bus service of level. Finally, the study results of deliberation system of opening bus route under subsidy imply that government decreases subsidy burden ratio on bus route under subsidy. The decrease of the ratio causes the decrease of social welfare as well as bus route headway, however the raises of the bus fare. If the analysis adds the restriction on bus fare, headway of bus route under subsidy causes substantially raise.
Moreover, this research analyzes the effect of different subsidy types. The subsidy types include：non-money subsidy, cost subsidy, deficit subsidy, performance subsidy, and price subsidy. According to three comparison bases, the five types cause different kinds of marginal benefit. The results indicate that subsidy marginal benefit of non-monetary subsidy has 1.46 times higher than that of cost subsidy. Price subsidy has 0.59 units higher than deficit subsidy. Performance indicators play an important role in comparison between types of performance subsidy and deficit subsidy. Furthermore, cost subsidy causes the more significant effect. If the government has enough funds, non-monetary subsidy causes the higher social welfare, the lower bus fare and headway.
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