Joseph E asks an excellent question in response to my last post about the new Swift BRT, in Snohomish County north of Seattle. Here’s the heart of it:
do you feel the wide stop spacing is a benefit? I was inclined to think the stations are too far apart. In comparison, commuter rail stops every 1 to 3 miles in most places (well, on the East and West coast), but always has an exclusive right-of-way, crossing gates, and high-speed operation between stations.
BRT should be capable of accelerating faster than diesel commuter trains, and obviously can stop much faster than even light rail. So why not have stations every 1/2 to 1 mile? It is much easier to walk 5 or 10 minutes to a station than walk to a local bus stop and transfer a mile down the road.
Arterial BRT can’t be compared to commuter rail. It belongs in a space between ordinary limited-stop buses and arterial light rail. And Swift is clearly at the lower end of that range: it’s running on the side lane, for example, where it will trip over turning movements, especially the zillions of driveway accesses into small businesses all along the route. In such settings, high-reliability exclusive-lane service pretty much has to be in the median, and that’s clearly not what this is.
A recent Seattle Transit Blog interview with King County Metro’s Karen Rozenzweig here (hat tip: Pantheon) is helpful for defining the kind of service this is. King County Metro, which serves Seattle itself and southern and eastern suburbs, is looking at a very similar product to Swift, called “Rapid Ride,” and she lays out the ideas pretty well.
So about the stop spacing. Why not stop every 1/2 mile, so everyone’s within a 1/4 mile of a stop once they’re on the arterial? The crucial fact of life here is that the distances people will walk vary quite a bit based on the quality of the service. For a fast, frequent service that will take them long distances, many people will walk over 0.5 mi and some will walk much further.
So if you put the stops close together, you are helping to make sure you don’t miss anyone, but at the same time you’re providing duplicate coverage to the people who will walk further. At the same time, you’re reducing the speed of the service and increasing its capital expense — especially on a system where the stations are really the main fixed-capital item. Don’t be too distracted by acceleration and braking times; they don’t make that much difference at this scale compared to the number of stops.
Stop spacing ends up being very political, and varying based on local conditions along the route. If you’re focused on long term urbanist outcomes, and are thinking about how the service will function once there’s been some redevelopment, fewer stops may be better, because you’ll concentrate development into nodes producing a more transit-efficient development pattern that supports the wide stop spacing into the long term.
Of course this is really bad for the people who are on the highway, a long way from a stop, not able to walk that far, and thus needing to use a local bus. Good BRT planning looks carefully at densities all along the line, and tries to have this impact only where the ambient density is fairly low, which means there aren’t many of those people. You’ll get need-based arguments from the people affected, but planners and politicians have to be trained to distinguish need-based arguments (I’m a nice person, and I really need the service) from demand-based arguments (we’re thousands of nice people, and we’ll use the service). BRT is about demand. Local buses and paratransit are there to serve needs.