Because the sprawl has become an emergent phenomena that is self reinforcing.
Are you familiar with conway's game of life?
What we have produced is a system of urbanization that, in a sense, behaves like a fire. Our cities don't properly increase in average density and land value in a smooth transition like you see in Europe and Asia. Instead, they're burning outwards leaving a growing circle of rot behind them.
You can create "fire" patterns in conway's game of life that take pristine space, and leave behind low density wreckage as the wave burns through. That's what I think we have created. There is no countervailing force to arrest the successive growth of rings around the burned out core.
I omitted one ring. In many American cities OUTSIDE the top 20, the stagnant CBD is ringed by by historic districts with strong zoning limits and high land values. In the top 20's these are usually slums with some gentrifying areas.
What occurs in the American city is that the lack of existing mass transit in the suburbs to begin with prevents the suburbs from increasing in density as they age. Even where zoning and historic districts DON'T inhibit the construction of increased density buildings, the lack of transit makes it untenable to increase the density because the roads (designed for suburban density) won't support it.
Building the transit during the densification process doesn't happen because that means clawing back land from existing owners to build transportation corridors that weren't planned.
Yes they are.
Now, consider: In that same space, the GTA manages to fit ten million more people than the total population of Texas.
This is why mass transit doesn't work in the US.
Because the sprawl has become an emergent phenomena that is self reinforcing.
Are you familiar with conway's game of life?
What we have produced is a system of urbanization that, in a sense, behaves like a fire. Our cities don't properly increase in average density and land value in a smooth transition like you see in Europe and Asia. Instead, they're burning outwards leaving a growing circle of rot behind them.
You can create "fire" patterns in conway's game of life that take pristine space, and leave behind low density wreckage as the wave burns through. That's what I think we have created. There is no countervailing force to arrest the successive growth of rings around the burned out core.
To put it another way, our cities are growing like this...
They are, but they don't exhibit the same pattern.
Here, I drew you a diagram.
I omitted one ring. In many American cities OUTSIDE the top 20, the stagnant CBD is ringed by by historic districts with strong zoning limits and high land values. In the top 20's these are usually slums with some gentrifying areas.
What occurs in the American city is that the lack of existing mass transit in the suburbs to begin with prevents the suburbs from increasing in density as they age. Even where zoning and historic districts DON'T inhibit the construction of increased density buildings, the lack of transit makes it untenable to increase the density because the roads (designed for suburban density) won't support it.
Building the transit during the densification process doesn't happen because that means clawing back land from existing owners to build transportation corridors that weren't planned.