Reducing transit bus emissions: Alternative fuels or traffic operations?

• Published in: Atmospheric environment (1994) 2014-06, Vol.89, p.129-139
• Main Authors: Alam, Ahsan, Hatzopoulou, Marianne
• Format: Article
• Language: English
• Subjects: Applied sciences; Atmospheric pollution; Compressed natural gas; Emission modeling; Exact sciences and technology; MOVES; Pollution; Prevention and purification methods; Queue jumper lane; Transit bus emissions; Transit signal priority; Transports and other
• ISSN: 1352-2310; 1873-2844
• DOI: 10.1016/j.atmosenv.2014.02.043

In this study, we simulated the operations and greenhouse gas (GHG) emissions of transit buses along a busy corridor and quantified the effects of two different fuels (conventional diesel and compressed natural gas) as well as a set of driving conditions on emissions. Results indicate that compressed natural gas (CNG) reduces GHG emissions by 8–12% compared to conventional diesel, this reduction could increase to 16% with high levels of traffic congestion. However, the benefits of switching from conventional diesel to CNG are less apparent when the road network is uncongested. We also investigated the effects of bus operations on emissions by applying several strategies such as transit signal priority (TSP), queue jumper lanes, and relocation of bus stops. Results show that in congested conditions, TSP alone can reduce GHG emissions by 14% and when combined with improved technology; a reduction of 23% is achieved. The reduction benefits are even more apparent when other transit operational improvements are combined with TSP. Finally a sensitivity analysis was performed to investigate the effect of operational improvements on emissions under varying levels of network congestion. We observe that under “extreme congestion”, the benefits of TSP decrease. •We estimated the effects of alternative fuels and transit operations on emissions.•Compressed natural gas (CNG) reduces GHG emissions compared to diesel.•As congestion levels rise, the emission reductions associated with CNG improve.•Transit signal priority (TSP) alone can reduce GHG emissions by 14%.•The benefits of TSP decrease under “extreme” congestion.