Importance of Automobile Mode Share in Understanding the Full Impact of Urban Form on Work-Based Vehicle Distance Traveled

Abstract

Vehicle kilometers traveled (VKT) has been widely used in regional planning as a key sustainability performance indicator. Many regional growth plans for reducing work trip VKT have been proposed, with a focus on land use development in employment centers. Despite the potential impact of urban form on the reduction of VKT, the fundamentals of how this takes place remain unclear. This study analyzes the relationship between urban form, VKT, and mode shares by examining office commuting patterns in the Greater Toronto and Hamilton Area (GTHA) through a structural equation modeling approach. The model supports the substantial impact of urban form on the reduction of VKT; however, it indicates that such an impact is made mostly through shifting modes, rather than directly on reduced travel distances. This model is then used to evaluate critically a regional growth plan for the GTHA, finding that strategies focusing solely on increasing land use densities in employment centers are not likely to reduce regional VKT significantly without also easing commuting auto dependency. Thus, it is recommended that more sustainable travel alternatives for workers in employment centers should be provided to achieve a sufficient reduction in VKT.

The Scarborough Survey: An interdisciplinary hybrid instrument to explore suburban challenges in Canada

“…An elevated rapid transit line provided extended access to the subway to the western side of Scarborough until August 2023 (5 stations in red, Figure 1), upon which time it was decommissioned absent any higher-order rapid transit alternative. A rapid transit busway will replace the subway by 2027 until the extension of the Line 2 subway arrives in Scarborough in 2030 (TTC, 2024), deepening their existing transit accessibility in the past 25 years (Allen & Farber, 2020).…”

“…While this is partly an outcome of the specific vehicle and fuel technologies used in transportation, it is also an outcome of the automobile-dependent urban context in which individuals, households, employment, and other activity destinations are located. Previous research has found that low-density and single-use neighbourhoods are associated with less frequent transit use and greater vehicle kilometres travelled by private automobiles (Cervero & Kockelman, 1997;Ewing & Cervero, 2010;Xi et al, 2020). Some have called for a "retrofitting" of the built form of the suburbs to become more dense, mixed-use, walkable, and transit-supportive (Cervero et al, 2017;Dunham-Jones & Williamson, 2008;Talen, 2011).…”

Immigrant settlement patterns, transit accessibility, and transit use

“…They have also both undergone polycentric development over the past several decades, with urban centres emerging in more suburban locations (Sarkar, Wu, & Levinson, 2020). These suburban centres however tend to have fewer transit connections and are typically reached more via car than public transit, compared to their historical cores (Xi, Allen, Miller, Farber, & Keel, 2020).…”

“…The dependent variable, transit mode share in a zone, is a percentage (bounded by 0 and 1), so we utilize generalized linear regression with a logit link function. The same type of model has been used in previous studies predicting neighbourhood-level transit mode share (Moniruzzaman & Páez, 2012;Xi et al, 2020). Our models are also weighted by the population in each zone.…”