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China's economic growth has been progressively moving towards reducing carbon intensity. In parallel, Japan has long been regarded as the pioneer of energy efficiency worldwide. Why have these two economic giants had such different experiences of carbon intensity in the past decades? A closer examination in both countries may hold vital clues, which are still very unclear. This paper compares the patterns of carbon intensity between China and Japan, in which we propose a bilateral-country decomposition framework by combining production-theoretical decomposition analysis and index decomposition analysis. The decomposition highlights the effects of emission factor, energy structure, sectoral structure, substitution among labor-energy and capital-energy, and technological progress. The results show that the energy structure, sectoral structure, and capital-energy substitution are the main drivers behind that China is much higher carbon intensity than Japan, accounting for 26%, 25%, and 38%, respectively. Yet, these effects also narrowed the carbon intensity gap between China and Japan over the years. Furthermore, the labor-energy substitution effect has generally decreased the carbon intensity gap. The technological effect has a minor impact on the carbon intensity gap per year, while it plays a dominant role in enlarging the carbon intensity gap over time. • An improved approach is proposed to decompose driving forces of carbon intensity. • The approach is applied to carbon intensity gap between China and Japan. • Potential energy intensity of each sector is uncovered by input substitution. • Enabling policymakers in developing countries to reduce carbon intensity. [ABSTRACT FROM AUTHOR]

Emissions from heavy urban traffic have been the most abundant components of urban air pollution in China. Compared to the fast increasing consumption of automobile, the growth rate of urban traffic infrastructure investment (UTII) is relative low. It is a controversial issue for the policymaker whether promoting the UTII could make a positive impact on reducing air pollution or not. This study is designed to test the relations between the UTII and air quality, using the data of 83 cities from 2000 to 2012. Based on the empirical results from the fixed effect model and dynamic panel data model, increasing the UTII could generally mitigate the air pollution, but the long-run and short-run effects are significantly different. In the short run, the UTII effect on air quality is −0.02, since the urban traffic infrastructure construction might cause more detours and road blockages, which would enhance the fine-particle emissions of the low-speed traffic. In contrast, the UTII could widen the roads and make the traffic system more accessible in the long run, so the estimated positive effect is about 0.05. The robustness tests about different regions and scales of cities are conducted. Policy suggestions are further recommended to reduce air pollution. [ABSTRACT FROM AUTHOR]

Traffic-related air pollution has become an urgent problem in many developing countries with rapid industrialization and urbanization. Traffic infrastructure construction, especially road reconstruction, is a prominent instrument of improving the road capacity and then affecting air quality. We employ the road area as the proxy variable of road infrastructure construction and further divide the road reconstruction pattern into lengthening pattern and widening pattern, respectively to evaluate the impact on urban air quality. The empirical result shows that the coefficient of road infrastructure construction represented by the road area is between −0.0818 and −0.0905, which means increasing road area has an emission-alleviating effect on air pollution. Moreover, we also find that the effect of road lengthening on air quality is better than road widening in the eastern China, but the improvement of road widening in the Central and Western China is better than the road lengthening. The result provides a valuable reference for policy recommendations on urban road infrastructure planning to improve air quality. • An empirical study is conducted to explore the effect of road construction. • Air pollution index is selected as the dependent variable to measure urban air quality. • An increase in road area can improve air quality. • Two road construction methods both have air pollution-reducing effect. • In the eastern cities, road lengthening is more effective in improving air quality. [ABSTRACT FROM AUTHOR]