Developing Speed Dependent Emission Factors Using on-Board Emission Measuring Equipment in India

Abstract

Vehicular emission models are important tools in several environmental impact studies. Although several studies have been conducted for emission control purposes, few attempts have been made on the planning side. For instance, long-term transportation network capacity improvement models do not explicitly consider emission in the objective function. Incorporating vehicular emission into the objective function is effective only if speed dependent emission factor is used in the estimation of emission. Although this issue is well addressed in the developed countries, owing to the heterogeneity of vehicles and absence of speed dependent emission factors the benefit from network investment is often underestimated in developing countries like India. Therefore, an attempt is made to explore the possibility of developing speed dependent emission factor for Indian conditions and vehicles. For accurate measurement an onboard test is conducted on typical vehicles; namely, a passenger car, a sports utility vehicle, and a truck. On board test equipment collected the data while the vehicle traversed with different speed ranges. The data obtained is processed and used for developing emission factor in the form of second degree polynomial with speed as the dependent variable. The emission factors for the three types of vehicles and for CO, CO 2 , NO X , and HC are developed. The results have been compared with Indian driving cycle based emission factors as well as UK based speed dependent emission factors for car in particular. The study gave a preliminary insight into the behaviors of pollutants with respect to speed. However, there is a need to develop such factor using large spectrum of vehicles and diverse driving conditions.