共享单车的外部性及其治理

共享单车在解决市民出行“最后一公里”难题的同时，也产生了一系列城市社会治理问题。作为一种由私人提供、有偿使用的准公共物品，共享单车负有一定的排他性与非竞争性，使市场无法完成外溢收益的内部化，表现出准公共产品特有的强烈外部性。结合外部性理论分析发现:共享单车产生外部性的过程可划分为生产与消费两个阶段，一方面，它能够激活传统自行车制造业、缓解交通拥堵状况、发挥出行替代作用且优化城市生态环境，综合形成产能效益、公共交通效益、社会效益、环境效益四大正外部性；另一方面，共享单车的生产与消费也使得传统经济行业受冲击、骑行安全问题频发、不文明现象泛滥、资金信息出现风险，综合产生了经济打击、交通隐患、道德困境、资金信息风险这四大负外部性。共享单车外部性内在化是纠正外部性，最终实现帕累托最优的过程，其关键在于通过宏观调控与市场机制相结合的多方共治框架、短期措施与长期规划相结合的长效机制，以期共享单车真正服务于城市发展、服务于居民生活。

Externalities of sharing bicycles and their governance

For solving the “last mile” problem of public travel,the concept of sharing bicycles can lead to several social issues. As quasi public goods that are utilised for both private and public use, sharing bicycles can be exclusive and non competitive. Thus, the market is unable to complete the internalisation of spillover earnings, showing the strong externality of productivity. While analysing externalities, it was found that the process of generating externalities by sharing bicycles can be divided into two stages: production and consumption. On the one hand, this process can lead to traditional bicycle manufacturing, alleviate traffic congestion, have an alternative effect, and optimise the urban ecological environment, all of which comprehensively generates four positive externalities of economic benefit, public transportation, social benefit, and environmental benefit. On the other hand, the production and consumption of shared bikes hurt the traditional economy, and increase safety issues related to bicycles, uncivilised behaviour, as well as financial information risk. These issues comprehensively generate four negative externalities of economic blow, traffic management, moral dilemma as well as financial information risk. Thus, the internalisation of the sharing bicycles’ externality is a process of correcting externalities and ultimately achieving the Pareto optimal. Thus, the key lies in the multi governance framework by combining both macro regulation and market mechanism and the long term mechanism that combines short term measures via long term planning, which truly help serve the urban development and urban life.