Abstract Manager

Transportation generates approximately one third of Canada’s greenhouse gas emissions, and is an increasing share of the total despite decades of effort to improve fuel efficiency and encourage mode shift. In addition to technical, institutional, and behavioural barriers, a contributing factor in our inability to reach emissions targets may be bias in our analytical techniques. Transportation emissions are exclusively quantified using attributional carbon accounting methods, which can distort the climate impacts of travel mitigation strategies. We have developed a new approach: a consequential framework to quantify the climate impacts of travel that more accurately represents the changes in emissions that result from changes in travel activity. Consequential accounting can be applied using marginal emission rates, which represent the change in total emissions that result from a unit change in travel activity. This presentation will describe how to estimate marginal emission rates and apply them to travel data from surveys or models. Results from a case study application to investigate household emissions from travel in metropolitan Vancouver are discussed, and contrasted with emission estimates from attributional accounting methods. We demonstrate that attributional accounting inflates the climate impacts of travel by public transit, particularly in areas with low-ridership transit services. Attributional accounting also under-represents the potential benefits of a shift away from travel by automobile. Shifting to a marginal perspective by applying a consequential framework to climate analysis for transportation plans, programs, and projects will improve their accuracy and sensitivity, and eliminate a systematic bias which can mislead decision-makers.