Investigating the isolated and combined effects of congestion, roadway grade, passenger load, and alternative fuels on transit bus emissions

Authors

Ahsan Alam
Marianne Hatzopoulou

Document Type

Journal Article

Publication Date

2014

Subject Area

mode - bus, technology - alternative fuels, technology - emissions, operations - crowding, planning - environmental impact, policy - congestion, policy - environment

Keywords

Transit bus emissions, Emission modeling, MOVES, Compressed natural gas, Passenger load factor, Grade, Random effects

Abstract

This study investigates the isolated and combined effects of network congestion, roadway grade, passenger load, and fuel type on transit bus emissions of greenhouse gases (GHG) through a simulation of transit operations and emissions along a busy corridor. We also test the effect of changing random seed on overall corridor emissions. We observe that positive grades have strong effects on emissions. Grade also causes other variables to become important such as passenger load. While an increasing passenger load on the bus increases emissions, we observe that the addition of each passenger influences the per-passenger emissions differently depending on the bus occupancy. When the bus is less crowded each additional passenger can decrease per-passenger emissions by 5% whereas the reduction becomes 1.2% when the bus is crowded. Finally, we observe that the reduction potential of compressed natural gas (CNG) compared to conventional diesel could reach up to 40% depending on speed, grade, and passenger load. CNG benefits increase with increasing congestion, and decrease with increasing grade and passenger load. The results of this study are most relevant to transit planners in the evaluation of potential operational changes with emission reduction potential and in the allocation of alternative fuelled buses along selected transit corridors.

Rights

Permission to publish the abstract has been given by Elsevier, copyright remains with them.

Comments

Transportation Research Part D Home Page:

http://www.sciencedirect.com/science/journal/13619209

Recommended Citation

Alam, A. & Hatzopoulou, M. (2014). Investigating the isolated and combined effects of congestion, roadway grade, passenger load, and alternative fuels on transit bus emissions. Transportation Research Part D: Transport and Environment, Vol. 29, pp. 12–21.