Is a grid system the most economically efficient way to lay out a downtown? Last week, I attended a talk by Prof. Robert Ellickson of Yale Law in which he made this argument. The talk was based on his article “The Law and Economics of Street Layouts: How a Grid Pattern Benefits a Downtown“. He was inspired to look into this subject by the exhibit “The Greatest Grid: The Master Plan of Manhattan, 1811-2011” at the Museum of the City of New York last year.
Ellickson contrasted two general models of street creation — bottom-up (created as people build and use the city), which tend to be unstructured (the main US example is Boston), or top-down (laid down by government), which tend to be more structured (most US cities, notably New York). Many cities have a combination of both.
Ellickson based his argument on the higher land values of properties in a downtown grid street system. To be honest, his evidence was fairly thin, so the paper is more a hypothesis than a proof. Ellickson suggested that a grid system is more valuable for three reasons:
- it’s cheaper to build rectangular buildings, in a rectangular block
- there are, apparently, significantly fewer disputes over property lines between owners of rectangular lots compared to irregular lots
- a grid system promotes greater social interconnection and interaction
It sounds plausible, but it would certainly need more thought and investigation before it can be said to be proven. (He says his theory does not address suburbs because they have different incentives and are more purely residential, but that might also be an interesting area of investigation).
The discussion of street grids also inspired discussion of block sizes, on which there has apparently been some work (there is in fact a Journal of Urban Morphology). He argues that there is a sweet spot for block size. Too large, and the land inside the block starts to lose value because it is too far from the street. Too small, and streets start to take up too much of a city’s surface area.
He also looked at changes to street plans — specifically, how often streets disappear. He found that streets are remarkably persistent — once laid down, it is hard to get rid of them, although grid streets are a little more persistent than non-grid streets. Alleys, on the other hand, come and go fairly easily.
An interesting tidbit he shared was that New York’s grid plan specifically rejected ovals and circles in its street plan (which planners often like because they create vistas – think Queen’s Park) because they tend to become exclusive and elite.
The discussion of street layouts naturally made me wonder about how Toronto’s old street grid developed. It looks to me like Toronto’s was implemented as a top-down grid on the large scale (main streets), but as bottom-up micro-grids, created by the owners or developers, within that large scale. That would explain why so many local streets don’t match up on the other side when they cross main streets. (Lower Manhattan, before the grid plan, was also a series of micro-grids that didn’t connect well).
The discussion also makes me wonder how it would apply to suburbs. They continue the pattern of creating streets bottom-up — largely laid out by developers — within an overall grid. Given the problems caused by their layouts, it’s troubling that streets are so difficult to change. But I also wonder if the economic efficiency of grids, if demonstrated, might encourage developers to explore using them even in suburbs.
Image from City of Toronto Archives