Uncovering JAPA

Retrofitting Suburban Arterials for Smart Growth

It is widely known that many cities and towns in the United States are car-oriented, and this is the case in other countries as well. But starting in the mid-1990s, there has been increasing consensus among planners and policymakers around the need to pursue smart growth. Central to smart growth is creating a walkable, transit-oriented urban form. Retrofitting suburban corridors through redevelopment and transit projects can play an important role in realizing this goal.

Toronto Corridors Analyzed for Retrofit Potential

In "Can We Retrofit Suburban Arterials? Analyzing the Walkability and Retrofit Potential of Four Toronto Region Corridors" (Journal of the American Planning Association, Vol. 89, No. 1), Paul Hess, Michael Piper, and Andre Sorensen examined four suburban arterial corridors in the Toronto region to measure and compare their urban forms and to examine how amenable areas with low walkability are to suburban retrofitting.

The corridors were intentionally selected to represent different planning periods and geographies (Figure 1):

  • Eglinton Ave E shows suburbanization patterns in the era of Metro Toronto when development was transitioning from prewar practices to more fully planned postwar models in the 1950s and 1960s.
  • Finch Ave E represents the development starting from the 1970s under a fully institutionalized Metro Planning regime, overlapping with the first one.
  • Winston Churchill Blvd was developed from the 1980s and into the 1990s after large-scale greenfield development had moved beyond the boundaries of Metro Toronto and into surrounding jurisdictions.
  • Oak Ave demonstrates development starting in the mid-1990s when suburban municipalities began explicitly adopting new urbanist planning models.
Figure 1. Case study corridors mapped against the period of urban development.

Figure 1. Case study corridors mapped against the period of urban development.

Suburban Corridor Walkability and Retrofit Challenges

They found that the walkability of corridors generally declined as modernist planning ideas were more fully implemented and then walkability generally increased as new urbanist ideas began to influence planning in the 1990s. However, over time, the retrofit potential declined across all corridors as patterns of lots and development became ever more static.

One of the interesting findings is that the planning and urban form of new urbanist corridors appeared to be even more controlled and static than those planned in the preceding eras. However, the authors suggest that given relatively high walkability, the inflexibility of the form may not be inherently problematic but does point to the difficulties of increasing walkability to higher and more desirable levels. It also points to the challenges of adapting new urbanist forms to unforeseen future needs, such as societal shocks that incur changes in mobility patterns.

Overall, the study shows the importance of analyzing forms of suburban corridors for planners to develop more tailored retrofitting strategies. As arterial roadway corridors present the potential to bring transit-oriented and walkable urban places near large areas of automobile-dependent suburbs, the study calls for more attention on the topic from practitioners and researchers.

Top image: Row Houses in Toronto's East End - iStock/Getty Images Plus - ihoe.

About the author
Jiwon Park is a master in urban planning candidate at Harvard University's Graduate School of Design.

March 9, 2023

By Jiwon Park, AICP