Factors driving reduction in CO 2 emissions from personal travel: A repeated cross-sectional analysis

This study identifies factors that drive the changes in CO2 emissions from personal travel in urban areas during 2006 and 2016 using repeated cross-sectional household travel surveys conducted in Seoul, Korea. We first estimated the daily travel CO2 emissions of every survey participant for each year based on travel itinerary records and estimated CO2 intensity for the travel mode. The results suggest that total CO2 emissions from personal travel in Seoul declined remarkably between 2006 and 2016, potentially due to reduced vehicle use, transition to non-motorized travel, improved vehicle technology, and eased traffic conditions. Two multilevel mixed-effect Tobit regression models were developed to identify the factors affecting CO2 emissions from personal travel for each year. The results suggest that some cohorts (e.g. males, 30s and 40s, small households, high-income groups, car owners) are likely to produce more CO2 emissions from personal travel consistently in 2006 and 2016. The changes in the estimated coefficients between the two years were also evaluated statistically, suggesting that some population groups (e.g. elderly, large households) are likely to reduce CO2 emissions from personal travel. The reduction in CO2 emissions by these groups may be correlated with continued investment in the public transportation system in Seoul. These findings provide an opportunity to gain a clear understanding of travel behavioral changes related to CO2 emissions from personal travel, with insights toward sustainable development.