The net greenhouse gas impact of the Sheppard Subway Line

Abstract

As cities work to reduce their total greenhouse gas (GHG) emissions, the transportation sector is lagging, accounting for a growing percentage of total emissions in many cities. The provision of public transit, and specifically urban rail transit, is widely seen as a useful tool for reducing urban transportation GHG emissions. There is, however, limited understanding of the net impact of new metro rail infrastructure on urban emissions. This paper examines the net GHG emissions the Sheppard Subway Line in Toronto, Canada. The GHG emissions associated with construction, operation, ridership and changes in residential density associated with the provision of the new metro rail infrastructure are assessed. These components are then combined and compared to calculate the net GHG impact across the study period, which extends from opening in 2002 through 2011. The GHG payback period is calculated. After nine years of operation, the Sheppard Subway Line is found to have nearly paid back its initial GHG investment in the optimistic case. The payback was due to the calculated mode shift from automobiles and changes in residential density and associated energy saving in the station pedestrian catchment areas. The payback period is very sensitive to the potential for induced demand to backfill the mode shifted automobile kilometres.

Temporal Assessment of the Embodied Greenhouse Gas Emissions of a Toronto Streetcar Line

“…The construction of public transit infrastructure is often associated with GHG emission savings given changes in travel behavior (Chester and Cano 2016;Saxe et al 2017). Existing research has calculated a GHG payback period, which quantifies the time required to recuperate embodied GHG emissions through travel behavior and/or land use changes.…”

“…Existing research has calculated a GHG payback period, which quantifies the time required to recuperate embodied GHG emissions through travel behavior and/or land use changes. However, most studies limit embodied GHG emissions to initial construction when calculating payback (Chester and Horvath 2010;Chester and Cano 2016;Saxe et al 2017). If rail infrastructure must be entirely rebuilt within 40 years, the embodied GHG that must be "paid back" is significantly higher than has been calculated in past work.…”

“…Research by Chester and Horvath (2009) found that, for rail systems, accounting for infrastructure and vehicle construction increases the overall GHG impacts of travel by a factor of 1.8-2.5. However, to date, examination of the GHG impacts of transit infrastructure has been hampered by limited access to construction data and even more limited assessment of the refurbishment and reconstruction needs over the life of a rail line (Chester and Horvath 2010;Hanson et al 2016;Saxe et al 2017). Most work in the field has been time independent and provides limited differentiation between the years and causes of emissions Horvath 2009, 2010;Hanson et al 2016;Kimball et al 2013;Li et al 2016).…”

“…Most work in the field has been time independent and provides limited differentiation between the years and causes of emissions Horvath 2009, 2010;Hanson et al 2016;Kimball et al 2013;Li et al 2016). A few recent studies have adopted a time-dependent approach (Chester and Cano 2016;Saxe et al 2017), which provides valuable information on the temporal distribution of emissions. The impacts of infrastructure provision on overall GHG emissions remain underexplored.…”

“…Recent studies have explored the life cycle environmental impacts of transit infrastructure (Chester and Cano 2016;Saxe et al 2017). Other research has focused on the embodied GHG emissions in buildings (Gantner et al 2018;Kaethner and Burridge 2012;De Wolf et al 2016).…”