Energy and Emission Benefit Comparison of Stationary and In-Vehicle Advanced Driving Alert Systems

Automobiles powered by fossil fuels are one of the major contributors to both criteria pollutant and greenhouse gas—in particular, carbon dioxide (CO2)—emissions. Previous studies revealed that unnecessary acceleration and hard braking in response to sudden changes of traffic signals may cause a significant amount of wasted energy and increased emissions. Altering the behavior of drivers approaching signalized intersections potentially could reduce energy consumption and emissions from motor vehicles without increasing travel time or delay. Two types of advanced driving alert systems (ADAS) are proposed: stationary ADAS [based on roadside infrastructure, such as changeable message signs (CMSs)] and in-vehicle ADAS [driven by advanced communication technology, such as vehicle-infrastructure integration (VII)]. These systems can help drivers avoid hard braking at intersections by providing real-time information on traffic signal status. A state-of-the-art modal emissions model is used to evaluate and compare the effects of these two types of ADAS on the reduction of vehicle fuel consumption and CO2 emissions. A numerical analysis of a single vehicle shows that ADAS can help reduce vehicle fuel consumption and CO2 emissions by up to 40% in the tested hypothetical conditions. The benefits of these systems are further investigated in a traffic simulation environment with various levels of congestion and posted speed limits. The simulation results reveal that both CMS-based ADAS and VII-driven ADAS can provide fuel and CO2 savings; VII ADAS offer greater savings in most cases.