汽车共享出行减少空气雾霾了吗?——基于滴滴出行大数据

Has car-sharing mobility reduced haze?: based on the big data of the Didi app

以雾霾为代表的环境恶化问题不仅增加了中国经济发展的成本,其在区域发展、社会等级之间和代际的分摊不公正现象还大大降低了人们生活的品质和幸福感。共享出行的出现促使人们由消费者拥有自己资产的生活方式向消费者共享资产的生活方式转变,不仅便利了人们中短途的出行,也增加了城市内部的生产生活集聚程度;但共享出行依然以汽车为载体,汽车尾气为雾霾的主要产生方式之一。鉴于此,文章以2017年滴滴出行开城城市的截面数据为研究样本探讨汽车共享出行对雾霾的影响机制。空气雾霾具有显著的空间溢出效应,在控制城市的经济、交通、地理、气象和政策变量后,以广义空间两阶段最小二乘法(GS2SLS)模型估计了汽车共享出行对雾霾的影响,分别以代表人类活动强度和范围的城市化深度(城市集聚)和广度变量(城市蔓延)为中介变量检验城市形态在汽车共享出行和空气雾霾之间的传导机制,并检验了基于城市层级的异质性。研究发现:(1)汽车共享出行规模与雾霾在空间上呈现显著的"正U型"关系,其最初的发展对雾霾具有显著的促降作用,但当发展到如北京、深圳等规模后会加剧雾霾污染。(2)新能源汽车占比的提升有利于减少雾霾,但不显著,目前新能源汽车对雾霾的作用机制尚不明确。(3)城市化深度是汽车共享出行减排作用的传导机制,这一结论在三线及以上城市中得以验证,四五线城市的传导机制不明显。(4)汽车共享出行的发展规模应与城市发展规模相适应,设计减排政策可以考虑从集聚的城市形态入手,减少城市的低效蔓延。

Environmental degradation,represented by haze,not only increases the cost of China’s economic development,but its unfair distribution among regional development,social hierarchy and generations has also greatly reduced the quality of life and happiness.The advent of shared mobility has prompted people to switch from a lifestyle in which consumers own their assets to a lifestyle in which consumers share assets.This not only facilitates people’s short-distance travel,but also increases the concentration of production and life within the city.But shared mobility is still based on cars,and vehicle exhaust is one of the main ways to generate haze.In view of this,this article used the cross-section data of the Didi app in 2017 to study the impact mechanism of shared mobility and haze.Haze has a significant spatial spillover effect.After controlling urban economic,geographic,transportation,meteorological and policy variables,the GS2SLS(generalized spatial two-stage least squares)model was used to estimate the impact of shared mobility on haze.Then we used the urbanization depth(urban agglomeration)and breadth(urban sprawl)variables which represent the intensity and scope of human activity as mediators to test the transmission mechanism of urban form between shared mobility and haze,and test the differences based on urban heterogeneity.The study found that:①The scale of shared mobility and haze showed a significant‘U-shape’relationship.Its initial development would have a significant effect on reducing haze,but it would intensify haze when it developed to a scale as large as Beijing and Shenzhen.②The increase in the proportion of new energy vehicles was conducive to reducing haze,but it was not significant.At present,the mechanism of new energy vehicles on haze is not clear.③The depth of urbanization was the main transmission mechanism of haze for shared mobility.This conclusion was verified in third-tier cities and above,and the transmission mechanism in fourth-tier and fifth-tier cities was not obvious.④The scale of car-sharing mobility should be compatible with the scale of urban development.The design of emission reduction policies can proceed from the form of agglomerated cities to reduce the inefficient spread of cities.