I'm looking for information on best practice precedents for parking.
The suburban area in which the site sits is an office-, retail- and residential-oriented TOD, with a very large suburban office component as well as a quite a bit of retail and multi-unit housing, developed beginning from the late 1970s. The TOD is already a regional transit hub. It will ultimately be served by several modal systems, several of which don't currently exist and are under planning or construction - urban rail (imminent), commuter rail (exists), BRT (coming soon), high frequency local bus - 30+ routes (exists), regional bus (exists), in addition to direct interstate highway access. Current transit modal share for the area is around 15%, although some commercial parcels are now reporting ratios as high as 30-35% or so for their workers and customers. The city would like to see the average transit modal share increased to the mid-30s or higher, over time, and even higher for new development immediately adjacent to rail links. Currently, the area has a parking ratio of about 4-5 spaces per 1,000 sq ft for office and retail and between 1 to 2.5 spaces per housing unit (all multi-unit), but that's biased toward older projects from the 70s and early 80s. Current code caps parking at 3 spaces per 1,000 sq ft for new commercial construction, specifies 1 space per housing unit irrespective of unit size and allows for 20% sharing between residential and commercial on top of this.
The client (a developer who controls about half the land in the TOD, all of which they plan to either develop anew or redevelop) thinks these current code ratios will still require them to construct way too much parking, citing that some similar TODs around the country now allow for ratios of or below 1 space per 1,000 sq ft (they cite stuff they know about in NoVA, etc). Their transportation planner believes that 3/1,000 is doable but they're pretty conservative and unwilling to recommend anything more aggressive than current code. Client strongly disagrees and wants me, as the land-use person and urban designer, to build a case for lower ratios. The city has decided they hate parking and are willing to discuss.
What do people think? What are the best practice precedents? Is there such thing as too low? Can we go to zero or near-zero for commercial space based solely on the unspecified future development of commercial parking structures?