building type selection

[fscottfoti]

Before I get started it's worth referring to the next generation developer model, which will solve many of these issues - UDST/urbansim#112. In other words, there's definitely a path to solve this the "right" way but I want to make sure we're aware of the current state of things and any near-term fixes that can be made.

The problem exists on the residential and commercial side in slightly different ways. First, the residential.

The issue is how to select a building_type from a land use. So we know the use is residential, we have an average price/sqft for residential and have density limits either through height, FAR, or DUA. So we get a "residential" building out at a certain density, considering the zoning, the costs of building at different heights, etc. The easiest way to map the land use to a building type - what we do now - is just to map based on density. So single family is a DUA < 12, townhomes are 12 < DUA < 24, and multi-family is DUA > 24. What I've noticed is that the current zoning I'm looking at doesn't have a lot of DUAs less than 12, so we're not getting a lot of HS out of the developer model. Anyway, this is working as designed, but the design might need to be improved. But for starters I'm just surprised there isn't more restrictive zoning even in very suburban areas.

On the commercial side, the problem is even more onerous. We get control totals here by sector, and we have sqft by building which we respect, and then we choose to develop commercial based on the right prices for the land use, and respect the sqft per building type, but we don't really have a mechanism to turn the employment control totals into demand for sqft of a certain land use. Do we really want to capture substitution of building types by a sector - or would we prefer to map sectors to a building type distribution for that sector (since there's only 6 high-level sectors) and thus get control totals for new commercial development by land use (the same way we have on the residential side) and then we can pick from profitable developments to meet that amount of development. Until then we get mostly office development because it gets the highest rents and then put sectors in office buildings that probably shouldn't be there. This is also the reason why we don't get retail at appropriate rates with the appropriate distributions. Of course retail location choice is a HUGE problem even on its own and we can leave that for another day.