Monday, April 4, 2011

BRT on the cheap using freeways

View Freeway BRT options in the Twin Cities in a larger map

[Edit 4/7/2011: Symbols with dots in them are supposed to indicate existing stops/stations. The colors are meant to be an indication of how easy it is to maneuver through an interchange to load/unload passengers. Green is supposed to mean minimal maneuvering, mostly going in a straight line or with an immediately-accessible turn-around area that is actively being used. Generally, green also overlaps with existing infrastructure. Yellow generally refers to diamond interchanges that are not currently in use (but probably could be), or other similar infrastructure (such as two half-diamonds a short distance apart with frontage roads in between). If an active, existing station has a yellow marker, it probably means that I think the buses using it need to make too many turns and go too far out of their way to load and drop off passengers—existing locations prime for an upgrade. Red refers to interchanges that would need infrastructure upgrades to support fast service, such as turnarounds or special bus-only lanes, but only for short distances. They are typically 3/4-diamond with a single cloverleaf or folded ramp, but I also included some SPUI interchanges and other things. I designated the Huron Boulevard bus stop used by Route 94 as red with a dot because it does exist, but only in the westbound direction, and it would be fairly difficult to upgrade that one.

I only spent a few hours poking at the map, so there are probably a number of interchanges that lack sidewalks and have other issues. Similarly, I may have missed a few existing stops, or misclassified a few things. Apologies—it's a bit of a work-in-progress.]

I've always wondered why metro-area bus agencies haven't made more extensive use of freeways to move passengers at higher speeds. There are numerous express routes which use them, of course, but they mostly make several stops in the suburbs to collect passengers, then run non-stop until reaching one of the downtowns. This makes the bus network pretty incomprehensible, since you can't immediately tell whether a service is only commuter-oriented or if it runs all day. I'd much rather see a system of trunk routes implemented with high service frequency, and collector buses running generally perpendicular routes.

But how much opportunity is there? By my count, there are probably 130 simple diamond interchanges in the Twin Cities which could have service implemented in no time flat, and another set of about 40 interchanges (mostly ¾-diamond which would need a turn-around zone for one direction) which could be fixed without too much effort—certainly each one would be a fraction of the cost of the 46th Street station on I-35W. That would make a pretty impressive network all by itself, and additional interchanges requiring more complicated infrastructure could be implemented later.

There are inherent drawbacks to putting service in a freeway corridor, such as noise and pollution, and the fact that accessing bus stops along freeway on- and off-ramps may require walking in front of a driver who isn't expecting to see any pedestrians. Annoyingly, it's also difficult to make connections between freeway-based services because most expressways in the Twin Cities use cloverleaf interchanges or other specialized designs that don't have convenient stopping points. It could work to re-route one of the services along surface streets for a mile or three, but doing that could dramatically slow down the service.

I dunno—I suppose people will say that the density just isn't there, and that's probably true. On the other hand, the average Hiawatha LRT passenger is drawn from more than 3 miles away from the route, so if you could build something that is just half as attractive as the LRT, it could draw quite a following.

Well, my biggest concern about all this is that it could draw riders away from using surface routes which actually go past walkable business corridors. It might not be so bad, though—how many people would become more interested in using public transit in general if a stronger core network could be created?


  1. We know that buses need to move faster when freeways are congested, either on the shoulder or (ideally) in HOV/T lanes. One potential constraint would be in corridors where there's a HOT lane on the leftmost lane of the carriageway, but exits are on the right. How would we accomplish arterial BRT on corridors like 35W and 394?

    I really like your ideas! I've thought about this myself. If the service can be speedy, and connect strings of transit stations in addition to other stops, it can also serve as more efficient off-peak service to transit stations. Took the 460 or 467 in to work but Happy Hour turns into all night? Take the Orange (or whatever) BRT south to your transit station. These lines can also through route and be combined on transit spines downtown. Think Chaska to Anoka via 212/62/35W/10, or Lakeville to Blaine via 35W, or Apple Valley to Roseville via 77/62/35W/36.

  2. It's unfortunate that the I-394 transitway was designed the way it was. Its current configuration is pretty much useless for accessing any sort of stations along the way. The 35W transitway is planned to extend farther north and eventually have a station at Lake Street, but I can't say when that will happen. The problems can be fixed, but will cost lots of money.

    Personally, I think that the short-term best option is just to run buses in traffic and make use of shoulder lanes as much as is necessary. Certainly transitways should be built and new access ramps added for them whenever possible, but even a slow highway is still way faster than any sort of transit on surface streets.

    Ideally, I don't think I'd even want to have freeway buses—I'd probably rather see a Curitiba-like BRT system on surface streets, or have bus-only grade-separated transitways. The freeway BRT idea is simply making use of the fastest roadways we have.

    Bus transit is always going to be slower than the prevailing speed of cars on the same road. The buses have to serve stops, while cars can go point-to-point. Compared to regular express buses that run non-stop from suburbs to downtown, freeway BRT routes making multiple stops would probably be considered a slight downgrade to the users going straight to downtown. This sort of system has to be viewed from the opposite side, however—it's a definite upgrade over trudging along at 15 mph on surface streets.