[kchoze]

Author here.

The principle you refer to here is Marchetti's constant. It's the idea that people will make decisions about where to live and work to achieve an average commute time of 30 to 45 minutes in general. So the faster transport options are, the farther from their workplace people will live.

And yes, IF you already have a complete network of urban freeways in a metropolitan region, THEN using fast transit options like commuter rail or commuter buses can help take people off of the highways, freeing up space for more people living even farther away. A good example of this "transit as highway capacity extension" approach is the commuter rails in North American cities that only go downtown during peak AM and go to the suburbs in peak PM, and not running the rest of the day. These forms of transit clearly exist to take pressure off of the highways at their most congested time, to free up the space for even more cars and perpetuate highway-oriented development.

Good transit options in the absence of highways have a different impact. And as you mentioned, transforming highways into expensive toll roads also can serve to deter sprawl built along them.