सिविल और पर्यावरण इंजीनियरिंग जर्नल

An Exploration of CO2 Emission Models for Horizontal Curves on Freeways

Abstract

Boya You, Fengxiang Qiao and Lei Yu

Global climate change attributed by CO2 emissions could seriously impact people’s daily lives. According to the statistics, road transport is one of the largest contributors to greenhouse gases. Simultaneously, the increasing number of vehicles, especially vehicle mileages traveled, will continue to induce more CO2 emissions. It is believed that the driving behavior is one of the most important factors that impact the CO2 emissions. However, some other factors may also contribute to the CO2 emissions, for instance, the geometric elements of a roadway. This paper explores the relationship between the horizontal curve radius and CO2 emissions on freeways from field tests under realworld driving conditions through the development of an Emission Factor Model (EFM). The prediction results were also compared with the measured CO2 emissions based on the default emission rates generated from Motor Vehicle Emission Simulator (MOVES). The modeling results indicate that the EFM has better performance for the estimation of CO2 emissions factors for horizontal curves on freeways under free flow conditions with a predicting error of 5.5%, which is much smaller than the one from a method directly estimated from MOVES (16.8%).