I wanted to make sure that people in the North Bethany development could easily get to their destination by transit, so I asked the county:
I noticed that TriMet has been involved in some of the discussions about N. Bethany and I was wondering if they (or any other source) has said how much density is required to support frequent bus service? If so, will N. Bethany be built to that density?
Ideally, North Bethany would be dense enough to support a frequent bus to the Willow Creek MAX stop, Sunset TC, and even downtown Hillsboro, Beaverton, and Portland. But it looks like we’ll be lucky to see the #52 serving any of the area. According to Washington County Planner Laurie Harris:
Phil Selinger, TriMet’s representative on the TAC, gave a presentation at the April 12, 2007 TAC and SWG meetings. The discussion is summarized in the following documents:
SWG meeting summary (page 2): http://www.bethanyplan.org/images/04.12.07swg_summary.pdf
TAC meeting summary (page 2): http://www.bethanyplan.org/images/04.12.07tac_summary.pdf
Phil said that North Bethany likely wouldn’t achieve densities to support high transit service [my emphasis. -peter] throughout North Bethany. In addition to density, there are urban design and development strategies that support transit, such as pedestrian-friendly amenities, sidewalks, and street connections. There is potential to extend Line 52 from PCC into one of the North Bethany neighborhood nodes or community center.
According to papers I’ve read (1, 2, 3) , there are some generally accepted guidelines for densities required to support transit. Here is what I’ve seen (note, the papers didn’t usually say, but I assume they are in units / gross acre):
- bus service becomes feasible at 7 units per acre
- frequent bus service becomes feasible at 15 units per acre
- rail transit becomes feasible at 30 units / acre
If Metro requires that new land brought into the Urban Growth Boundary be developed at 10 units / net acre, how come most of North Bethany won’t support at least infrequent buses? The reason is that the density they are looking at works out to be about 5.75 units / gross acre (equivalent to 10 units / net acre, when you don’t count land used for open space and roads), which isn’t enough to support transit. However, they plan on concentrating higher density development near the main civic center at Kaiser Rd so they can build low density sprawling suburbs on the rest of the site – this might be enough to support transit to that area.
I think the county needs to think more about the proper density for the site. Here are some questions I still have:
- Is there enough office/commercial to generate mid day trips to sustain frequent (or even infrequent) during non-commute times?
- If a certain level of transit becomes feasible at a given density, how much higher does the density need to be before that level of transit will usually be successful, or even pay for itself?
- How much of a given density is required? If most people will only walk 1/4 of a mile to a bus stop, how many people should be within 1/4 of a mile to support that stop, and how many such stops are needed along a service corridor?
- I’m guessing that if driving were more expensive, even lower densities would support transit. How much more would driving need to cost for 5.75 units / gross acre to support frequent service?
- Can we prove that for the lifetime of the houses (say 100 years), we will always have cheap personal transport? Oil sure looks like it is running out and nothing else promises to be as cheap or easy. If we know we’re running out of cheap oil, is it really appropriate to build at such low, automobile dependent, densities?
Vagabond Shark 