Discussion

From the analyses in this study, it is seen that the resident samples in the two case cities have good education level and thus are more open to strategies for global climate change mitigation. Most commuters working in the private companies are sensitive to the cost of commuting. It is also found that a high percentage of commuters own houses/apartments; therefore, the probability of changing their house locations is low, especially in the short term. The increase in CO2 emissions by commuters during the fast development period of a city is mainly due to travel mode changes and commuting from newly developed areas. Avoiding the sharp increase of car use, implementing TOD pattern at the early stage of the land development, and providing outstanding public transport service are important to reduce the commuting CO2 emissions.

It is also seen that the vehicle occupancy is an important factor of commuting CO2 emission in both China and India. Maximizing the vehicle occupancy of cars, normal coach, and taxis could reduce commuting CO2 emissions by as much as 50 %; decreasing the vehicle occupancy could increase commuting CO2 emission by as much as 66.67 %. Therefore, avoiding smaller vehicle occupancy is critical to control the increase of commuting CO2 emissions.

The analyses show that the characteristics of the high emitters are car availability, high income, working in the foreign company, and living in the outer areas/along the ring roads or far away from the bus stop. Reducing their emissions is important in both China and India. The outer areas of a city usually have better road conditions, lower service level of public transport, limited rail transit, or bus rapid transit to the central area of the city; it is hard for commuters to use travel modes other than self-driving, which leads to high commuting CO2 emissions. Therefore, the adjustment in urban planning, construction of rail transit, or rapid bus routes in the outer-inner area directions, as well as cycling and walking system, public transport service level improvement, and avoiding fast increase of car uses are the keys to low-carbon urban transportation development. In Chinese and Indian cities, the implementation of transportation pricing, transportation management, and public transit priority policies can guide commuters with high income to use public transportation and make them less car-dependent.

Traffic congestions already exist in the central areas of the cities in both China and India. How to increase the mode share of public transport and to reduce travels by car is a challenge for city leaders. There is a need to balance the overall efficient development of the city and the ability to drive in the central area of the city.

The larger emissions and longer commuting distances in Bangalore indicate that Indian cities should focus on high density and compact development, which can reduce average commuting distance, and can also improve public transport operations and service levels since the lower density, sprawled, and decentralized urban form has caused inefficiencies for the public transport. The use of clean energy vehicles in Xi’an is another reason for the lower commuting CO2 emissions. In Xi’an, buses and taxis are driven by compressed natural gas (CNG); metros and two-wheelers are powered by electricity. These can help reducing the commuting CO2 emissions to some extent, which can be learned by Indian cities.

In addition, even though Xi’an is a good example of compact urban development pattern compared with Bangalore at present, if Xi’an continues to develop under this pattern in the future, the central area will suffer from increasing traffic pressures and increasing transporta-tion CO2 emissions. An alternative strategy is to control the development intensity in the central urban area and try to apply a multicenter strategy for the urban development.