Low carbon cities: Land use and transportation interventions
通过四篇前沿研究，探讨中国土地利用与交通政策如何影响出行模式和碳排放，为规划者提供减排策略参考。
In 2014, carbon emissions in China almost doubled those in the U.S. (Olivier, Janssens-Maenhout, Muntean, & Peters, 2015), although per capita emissions were much lower in China. The transportation sector accounted for 6 percent of carbon emissions in China in 2012 while 32 percent of carbon emissions in the U.S. were attributable to the transportation sector (Liu, 2015). This contrast implies that carbon emissions from the transportation sector could grow substantially in China, imposing enormous environmental challenges. As urbanized areas have expanded and auto ownership has exploded in China (Gao et al., 2016; Wu, Zhao, & Zhang, 2016; Huang, Cao, & Cao, 2016), a few questions have emerged: Will China follow American-style patterns of suburban sprawl and travel? How can China achieve sustainable transportation through land use and transportation policies? What is the relationship between travel modes and greenhouse gas emissions? These questions are particularly important as China continues its industrialization and unprecedented urbanization (Cole et al., 2011). According to the data from the World Bank (2016), the fraction of Chinese population living in urban areas has increased from 36 percent in 2000 to 54 percent in 2014. The Chinese government expects a rate of 60 percent by 2020, as indicated in the National New-Type Urbanization Plan (2014–2020) (http://www.gov.cn/zhuanti/xxczh/, accessed on February 28, 2016). How China accommodates those new migrants to urban areas and meets their daily needs will greatly affect transportation-related carbon emissions (Zhang, Cao, & Ramaswami, 2016; Liu, Wu, Wang, & Wei, 2011). Land use and transportation policies play a critical role in reducing vehicle miles traveled and associated carbon emissions (Salon, Boarnet, Handy, Spears, & Tal, 2012; Cao, Mokhtarian, & Handy, 2009; Boarnet & Crane, 2001). Land use planning and policies affect how a region, city, or neighborhood develops. Transportation infrastructure investments shape urban form over the long term (Xu et al., 2016). The buildings and infrastructure being constructed now will last for decades and even centuries. Therefore, early interventions in urbanizing China could have substantial impacts on carbon mitigation (Huang, Cao, Cao, & Yin, 2016, Huang, Cao, Yin, & Cao, 2017). This special issue includes four cutting-edge studies regarding the impacts of land use and transportation policies on travel patterns and associated carbon emissions. In an aggregate study of 161 cities in China, Sun, Zhang, He, and Wang (2017) examine the influence of city characteristics on auto ownership and mode choice. They conclude that keeping high-density development can be effective in reducing growth in auto ownership, and that the government should prioritize transit investments rather than road capacity expansion to promote transit use and discourage auto use. Contrary to findings in developed countries, job-housing balance and polycentric urban form do not appear to lower auto ownership and auto use because of the specific context in China. Using a 2007 household travel/activity diary in Beijing, Xiao, Lenzer, and Chai (2017) explore the distribution of household travel-related carbon emissions (HTCE) within and between neighborhoods. They find that socio-economic status dominates HTCE. Furthermore, density, diversity, metro accessibility, and proximity to city center are negatively associated with HTCE. However, they conclude that one-size-fits-all strategies are inappropriate for carbon mitigation because the built environment effects on carbon emissions vary across different neighborhoods. They call for a new governance framework to achieve effective and equitable transportation policies. During the past decades, China has transformed its railways, both by extending the system into previously under- or un-served areas and by accelerating rail speeds with what is now the world's largest network of high speed rail. Using panel data from 1993 to 2012, Li and Loo (2017) investigate the competition between railway and air transport resulting from China's recent railway development. They find that both system extension and acceleration (higher speeds) have negative associations with the number of air passengers between city pairs. However, a segment analysis shows that the associations for long-haul city pairs are insignificant. Overall, they conclude that rail development achieves approximately a 7 percent net reduction in carbon emissions. Boarnet, Wang, and Houston (2017) adopt a before-after treatment control design (not commonly seen in the literature on land use and travel behavior) to study the impacts of deploying a light rail transit (LRT) line in Los Angeles on household vehicular carbon emissions. Using the data from 160 households across two waves, they find that residents in station areas produce about 27 percent fewer emissions than those who live farther away from stations, and the effect of the LRT on vehicle carbon emissions is about 3.1 kg per day. Therefore, rail transit has great potential to reduce travel-related carbon emissions. The quasi-experimental design also represents a methodological advance beyond most existing studies. It is worth noting that this paper was edited by a member of the journal editorial team, not by the special issue guest editors. We hope that this special issue provides scholars and practitioners with a better understanding of the effects of land use and transportation planning and polices on carbon emissions, and the strengths and weaknesses of different research designs. The case studies can help them in planning and deploying land use and transportation policies in China, as well as in the world. The four papers were presented at the international conference on “Low Carbon Cities – Land Use and Transportation Interventions” at Shaanxi Normal University, Xi'an, China, on June 12–13, 2014. Dr. Xiaoshu Cao and Dr. Jason Cao jointly convened the conference, which was sponsored by Center for Land Resources Research in Northwest China, Institute of Transport Geography and Spatial Planning, Shaanxi Normal University and Humphrey School of Public Affairs, University of Minnesota. Dr. Xiaoyan Huang and Dr. Jiangbin Yin helped conference organization.