Analysis of the influence of geometric design consistency on vehicle CO2 emissions

Abstract

Highway vehicles driving on rural roads account for more than 50% of all CO2 emissions produced by the transportation sector in Europe. Although the policy measures to mitigate Greenhouse Gas emissions are increasing, these do not include policies aimed at reducing emissions by means of highway geometric design, which significantly influences drivers’ speeds and accelerations and, consequently, plays a major role on fuel consumption and emissions.Therefore, the main objective of this research is to study the influence of the geometric design consistency on vehicle CO2 emissions. To do this, continuous speed data were collected on 47 homogeneous road segments by means of Global Positioning System devices. Vehicle CO2 emissions were estimated by applying the VT-micro model, whereas geometric design consistency was assessed considering different global consistency models.As a conclusion, vehicle CO2 emissions decreases as the consistency level of a homogeneous road segment increases. Specifically, a good consistency road segment has been found to present an emission rate 20–30% lower than a poor-consistent one. Therefore, the design of consistent roads allows, in addition to maximize road safety, to help to achieve more environmentally sustainable highways, reducing CO2 emission production.