Introduction

The Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report stated that recent global warming, sea level rising, and glacier melt were mainly caused by greenhousegas (GHG) emissions generated by human activities (IPCC 2007). Among the GHG emissions, carbon dioxide (CO2) is the single most important anthropogenic greenhouse gas which contributes about 65 % of total GHG emissions (WMO 2014). The transportation sector is a major source of CO2 emissions and currently contributes 20–25 % of global CO2 emissions. Its global share is projected to rise to 30–50 % by 2050 (Brand et al. 2013). It is estimated thatthe most targeted measure to reduce GHG emissions in an urban development context should aimed at reducing transportation CO2 emissions (Norman et al. 2006).

China and India together have more than one third of the world population and are two emerging economic giants of the developing world. There exist a group of cities in China (ranking between 5th and 65th; Beijing, Shanghai, Shenzhen, and Guangzhou not included) and in India, which are not the largest cities but are among the fastest growing cities in the world (Jones Lang LaSalle (JLL) 2015). The total population of these cities in China exceeds300 million, larger than the total population of United States (US). The total economic output of these Chinese cities is ca. $8.6 trillion, accounting for 9 % of the global output, and is expected to reach $15 trillion (15 % of the global output) in 2025. Now, China and India areexperiencing rapid urbanization and motorization (Pucher et al. 2007; Han 2010). CO2 emissions from transportation sector account for a large percentage, about 8 % of total CO2 emissions in China (Wang et al. 2011) and 32, 17, 13, 19, 43, 56, and 25 % of total CO2 emissions in Delhi, Greater Mumbai, Kolkata, Chennai, Greater Bangalore, Hyderabad, and Ahmadabad of India, respectively (Ramachandra et al. 2015). Commuting traffic is a major part of urban traffic and has been viewed as the most important traffic in the urban transportation (Meyer and Miller 2001). Commuting trips account for 51.6 and 67 % of the urban
passenger transportation in Xi’an and Bangalore, respectively (Mamatha and Madhu 2007; Xi’an City Traffic Management Committee and Chang’an University (XCTMCCU) 2012). The increase of CO2 emissions produced from commuting trips will be huge in these Chineseand India cities during the fast urbanization and motorization and thus may cause severe impacts on the global climate change.

Xi’an and Bangalore were chosen as the two case study cities for their representativeness ofmajor Chinese and Indian cities. Also, China and India are both rich in history and culture. Xi’an and Bangalore are typical cities with many heritages, rich cultures, and protected historical center districts. The two cities need to accommodate old traditions and modern development during the rapid urbanization and motorization (Ramachandra and Shwetmala 2009; Ramachandra et al. 2012; Wang et al. 2013, 2015).

Previous studies have found that socio-economic characteristics of individuals and households are related to transportation CO2 emissions, including age, education level, car availability, occupation, and income (Carlsson-Kanyama and Lindén 1999; Brand and Boardman 2008; Weber and Matthews 2008; Susilo and Stead 2009; Brand and Preston 2010; Ko et al. 2011; Brand et al. 2013; Büchs and Schnepf 2013). Households in rural, suburb, and urban districts have different levels of transportation CO2 emissions (Moriarty 2002; Troy et al.2003; Nicolas and David 2009; Ko et al. 2011; Xiao et al. 2011; Liu et al. 2012; Büchs and Schnepf 2013). Furthermore, straight line distances from the household location to the city center have been found to be correlated with vehicle kilometer traveled (VKT) and the transportation CO2 emissions (Miller and Ibrahim 1998). Previous research is short of comparative analysis between similar cities experiencing rapid economic growth, urbanization, and motorization in China and India, which are crucial for the global climate change. Also, the impacts of the urban spatial characteristics on the transportation CO2 emissions in the previous studies focused on the scattered household locations, not on the entire city.

Therefore, the goal of this study is to analyze the characteristics and the changing trends ofthe commuting CO2 emissions in Chinese and Indian cities during the process of the rapid economic growth, urbanization, and motorization. The study analyzes the characteristics, spatial distributions of commuting CO2 emissions, and their relationships with individual/ households’ socio-economics, travel activities, and urban spatial characteristics in the entire urban area of Xi’an and Bangalore. Based on the analysis and the findings, several strategies are proposed for the reduction of transportation CO2 emissions. This study will be useful for the low-carbon transportation development in Chinese and Indian cities and will also be a goodreference for other similar cities in the developing world. Therefore, it is important for the global climate change mitigations.