Adam Belz in the Star Tribune writes: Study says Blue Line’s development impact is minimal, discussing a recent study by Sarah West and Needham Hurst of Macalester. I get quoted:
“My first sense is the Green Line is a better line,” said David Levinson, a civil engineering professor at the University of Minnesota. “It’s going to a denser area.”
Levinson said that the Green Line — and any subsequent additions to the light rail system — will also improve the value of land along the Blue Line, thus making it more ripe for development as the rail system grows and more people use it.
“That positive feedback system sort of kicks in, and it reinforces the growth,” Levinson said.
Are accessibility and mobility complements or substitutes? I have a mental model a graph with a y-axis as density, and x-axis as mobility, where the Northeast corner would be high access: high density multiplied by high mobiilty.
This system behaves differently by modes. For transit, cities arrange themselves on a line from the southwest to the northeast (a positive feedback loop between supply and demand). For auto cities arrange on a line from the southeast to the northwest (a negative feedback loop between congestion and demand). Using data one could place specific cities on the graph. One expects places like New York and Hong Kong in the northeast corner, most US cities in the southeast corner, small developing-world cities without widespread adoption of modern automobile or transit technology in the southwest corner. Depending on where you draw the threshold, it is hard to see too many places in the upper northwest corner, as it would be difficult to grow to have high density without mobility. (Why would the city grow without the accessibility advantages?)
Accessibility is a good, but it is not a good without costs, and there are limits to how much people are willing to pay for access. It may also suffer from diminishing returns, beyond a point each unit of accessibility is worth less and less. Places like Minneapolis have yet to reach that point, but surely there are places that have.