Abstract Manager

​​​​​​This study examines greenhouse gas (GHG) emissions associated with household travel in Vancouver, Canada using both consequential and attributional carbon accounting frameworks, and investigates relationships with personal, neighbourhood, and contextual factors. Most analyses of GHG emissions from travel use an attributional carbon accounting framework by assigning vehicle emissions to vehicle occupants. The alternative is consequential carbon accounting, which aims to quantify the impacts of individual travel decisions on total system emissions, rather than to distribute emissions among system users. The attributional approach is easier to apply but consequential accounting is generally seen as more appropriate for policy analysis and to inform decision-making.  We apply a consequential accounting framework that shifts from using average to marginal emission rates for personal travel.  The importance of this distinction can be intuited by considering a low-occupancy city bus. The attributional approach would be to assign bus emissions proportionally to all occupants using the average bus emissions per passenger. But the average emissions per passenger are much higher than the additional (i.e., marginal) bus emissions if one additional passenger were to choose to ride the bus.

Our analysis reveals that most GHG emissions (97%) associated with personal travel in Vancouver are generated by automobile use, and a large share (41%) are from non-operating fuel and vehicle life cycle phases. We estimate average GHG emissions from travel of 10 kg CO₂e per person per day and 25 kg CO₂e per household per day. Greater neighbourhood walkability and regional transit access are associated with lower GHG emissions, even after controlling for factors such as income and vehicle ownership. The difference in estimated GHG from consequential versus attributional accounting methods is small in aggregate (3% lower), but large for individuals who use public transit. For example, consequential emissions are half as large as attributional emissions for 14% of trips (mostly by transit), and consequential emissions are half as large as attributional emissions for 11% of persons and 12% of households (mostly heavy transit users). We demonstrate equity implications of the GHG accounting framework applied for a carbon pricing scenario. Lower-income people, renters, and those who do not own a motor vehicle would disproportionately benefit under consequential versus attributional accounting methods, while older travellers would see an increased relative carbon tax burden.