Last time, I declared my intention to outline a zoning code that would make it easier to fulfill urbanist goals like supporting transit and the ability to walk to things, reducing vehicle kilometers traveled, conserving open space, and so forth. So, allow me to follow through and explain the idea behind my zones in more detail. I will implicitly use the City of Los Angeles Code as a reference point in some cases based on this document.
Mixed Use Low Density Zone (MU-1)
Right off the bat let me explain that I have a different concept of "low density" than most people do. Cities should have enough density, or at least permit enough density, to support at a minimum convenient bus service throughout their territory. That means the lowest density zone has to allow densities greater than those of a typical southern California suburb (my baseline for an urban form that can't support convenient transit service, at least without massive subsidies).
I would like to permit buildings up to three stories or about 15 meters (1 meter = 3.3 feet) in this zone not including a story of additional height (about 4 meters) added by a parking garage. Front and rear setbacks would be established, but would be modest, not more than three meters in either direction. Side setbacks would be established for detached houses (say 1 meter). I would set a very low minimum lot size: 200 square meters (2,153 square feet) allowing for the construction of economical and denser small-lot detached housing and rowhouses.
With regard to residential uses, this zone would permit detached houses, rowhouses, apartment buildings, mobile homes, houseboats, you name it, basically any kind of housing except a structurally unsound shack. Commercial uses would be allowed here as well: retail stores, restaurants, offices and the like. Industrial uses with low impacts would also be allowed. These would pass through a conditional use permit (CUP) process to ensure that their impacts (like noise and emissions) are low. Other uses passing through a CUP process would include things that are typically controversial like strip clubs (adult oriented businesses), businesses that sell alcohol, or businesses that are trying to maintain night hours (past 10pm).
Basically, you would be allowed to build a 1950s suburb in this zone if you wanted to, but you would also be allowed to build a low-rise mixed use main street, a big step up from what typical R-1 zoning allows in most places. You could have shops sprinkled in with homes and give people a fighting chance to walk, and you could build housing types that could support frequent transit service.
Mixed Use Medium Density Zone (MU-2)
This would be a more permissive zone than MU-1. Basically everything I said about MU-1 applies here except that you can build taller. I would set the height limit at 20 meters not including two stories (8 meters) of additional height used for a parking garage. This translates roughly into a six story building with retail on the ground floor as a maximum.
You would need some traditional light-entry regulations here for apartment buildings that form a continuous street wall.
Mixed-Use High Density Zone (MU-3)
Everything I said about MU-2 except I want to permit up to a 10-story building by right here. Therefore the height limit would be 32 meters for by-right projects, plus 12 extra meters for three stories of parking. For buildings taller than 32 meters there would be a CUP process so that people could regulate things like the amount of light that gets to the ground.
High-Impact Industrial Zone (HI)
I think there are some industrial uses whose harmful effects can't be regulated away at the present time and hence deserve automatic separation into their own zone. What I have in mind is things like a smoke belching factory, a loud assembly plant, or a major seaport. To the extent that this stuff is allowed to exist at all it should be in this zone. Environmental justice issues will come up in terms of where you locate these zones. This zone would allow shops, restaurants, and offices by CUP, but not any type of housing.
Parks, Agriculture, and Conservation Zone (PAC)
What it sounds like. Land would be specified with a sub-category to clarify its intended use. The intent here is for the municipal entity (political boundaries permitting) to preserve farmland and non-human natural habitat, establish urban parks and urban farming areas. 5% of parkland would be permissible for use as a community garden by right by an organization certified by the municipal entity and open to public participation. Perhaps a higher percentage would be allowed by CUP.
Per Shoup's ideas minimum car parking requirements increase our car dependency, hence they don't exist in this system. Instead, this system implicitly favors managing parking through prices. I don't want to set a parking maximum either, but I do want to discourage the excessive construction of parking by forcing a CUP for parking above a given level. I would define this by lot coverage. If parking takes up more than 50% of the lot in MU-1, 25% of the lot in MU-2 or 10% of the lot in MU-3, or 5% of the lot in PAC, you would need to get a CUP.
Bike parking minimums are an interesting issue that I have not made up my mind on. One approach might be to require that 10% of any area used for parking in MU1-3 or PAC (probably a lower percentage for HI) be used for bike racks that meet performance criteria set in consultation with bike activists.
Well, that was a mouthful. I actually want to follow this up with a third part, which will deal with pitching this idea to the public. In many parts of the real world this would be a tough sell, and the best planning is collaborative, not dictatorial. So, next time I will wrestle with the idea of how to win people over to this and how it could be the basis for some kind of compromise.