I recently stumbled on a map I made last year that plots present and proposed transit lines against population density. Density shown at the level of the city block using information from the 2011 Census.
Higher-density areas — those where the density is above 50 people per hectare — are shown in pink. Lower-density areas are shown in blue. Very low-density areas, which are typically employment lands and utility corridors, are white or grey. The threshold of 50 people per hectare is considered by some to be the minimum threshold for the provision of frequent-service transit.
What the map shows, I think, is that the case for surface LRT over subways is strong along the corridors proposed by Metrolinx and the TTC. The proposed LRT lines along Eglinton West and East and Finch would largely run through lower-density areas. Much of the existing subway system runs through broad areas of high density corresponding to the prewar city. The underground central portion of the Eglinton Crosstown line also runs through this zone.
While some corridors and transit station areas (but not the broader residential areas that would feed into them) have been intensified over the past 20 years — the North York City Centre area, the Sheppard corridor east of Yonge, and the Kipling/Islington Station areas — I’m not convinced that this can be replicated, at least anytime soon, in the blue zones where Mayor Ford wants to run subways.