The benefits of public transit in terms of reducing transportation-related greenhouse gas (GHG) and air pollutant emissions is a topic that needs little introduction. The literature swells with studies comparing per-passenger emissions in transit with emissions from single occupancy vehicles, stressing the importance of increasing transit ridership. We argue that increasing transit ridership is not sufficient to achieve meaningful emission reductions at a regional level. In Montreal, transit operations and technology are in dire need for improvement and additional reductions in transit emissions largely depend on the types of fuels used and driving conditions. We microsimulated the operations and emissions of transit buses along a busy transit 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. However, the benefits of switching from conventional diesel to CNG are less apparent when the road network is uncongested. As congestion levels rise, the emission reductions associated with CNG improve. We also investigated the effects of bus operations on emissions by applying several strategies such as transit signal priority (TSP), queue jumper lanes, and relocations of bus-stops. Results show that TSP alone can reduce 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.