Tuesday, April 21, 2015

Transit versus the overly-accessible freeway

In the run-up to construction of the Green Line between Minneapolis and Saint Paul, neighborhood activists spent a huge amount of effort to get three extra stations included on the route at Hamline Avenue, Victoria Street, and Western Avenue. These extra stations cut the distance between stations in half on that section, from one mile down to half a mile. This put nearly all of the buildings that face the Green Line on University Avenue within a 5-minute walk of the stations.

Getting that change to happen required advocacy work all the way up the chain of command for transit projects in the United States. In early 2010, the Federal Transit Administration changed the rules to de-emphasize a calculation called the Cost-Effectiveness Index (CEI) while adding an option to include livability as a factor. The change didn't just affect the Green Line, but meant that any other projects around the country could also benefit.

Considering that tremendous battle, it's amazing to see that on-/off-ramps to surface streets on Twin Cities freeways—the car equivalent to stations on a transit line—are often spaced less than a mile apart. In the map I made above, around 40% of the area's ramps are spaced one mile apart or less, and the great majority—about 85%—are less than two miles apart.

The shortest distance I found between two full interchanges is in Golden Valley by the headquarters for General Mills. It's about 0.3 miles along Highway 100 between Olson Memorial Highway (MN-55) and Shelard Parkway/Betty Crocker Drive.

The ramps at Shelard/Betty Crocker are also very close to the interchange between MN-100 and Interstate 394, though in making the map, I ignored exclusive freeway-to-freeway interchanges, since they don't provide any access to surface streets.

The longest stretch of closely-spaced ramps appears to be along MN-36 between Cleveland Avenue and Lexington Avenue—five interchanges on a two-mile stretch of highway, each a half-mile apart.

Now take a look at this presentation board from the Robert Street Transitway study and the station spacing suggested for each mode. It's head-scratching to see these ranges and compare them to what we expect when building infrastructure for cars.

For highway bus rapid transit services in particular, the suggestion is to space stations about two miles apart. There isn't necessarily anything wrong with that, particularly when highway BRT is laid on top of a system that already has closer stop spacing, but it is striking to compare it with a freeway system where most interchanges are much more tightly spaced.

I'm of the opinion that most of the Twin Cities bus network has stops that are packed too close together—usually around 1/8th of a mile apart on local routes, and sometimes even less. This isn't a huge problem on less-used and less-frequent routes, but busy lines are made interminably slow when they need to stop every block (and sometimes even more often than that!), but buses that run every 10 minutes or less are typically busy enough to need their stops spaced out a bit.

Two main problems arise when transit lines have closely-spaced stops: First, passengers get on and off at stops that are as close as possible to their destinations (good for them, but not always so good for the system). Second, passengers can end up making nonsensically short trips, such as waiting 5 or 10 minutes for a bus that will take them a quarter-mile down the road—a distance that can be walked in 5 minutes.

Limiting the points of access reduces those issues and makes for smoother trips. Yes, it is an inconvenience for some, but it tends to provide benefits to far more riders than it hurts.

Would similar effects be possible by spacing out some of our freeway access points? Can traffic congestion on highways be alleviated by encouraging some of the extremely short trips to happen on surface streets instead?

In urbanized areas with valuable land, this might be a simpler and better alternative to highway tolling, which have historically required toll plazas (difficult to fit into urbanized areas, although they are less necessary today due to RFID and other technologies that don't require physical payment).

Interstate 94 between downtown Minneapolis and downtown Saint Paul has a fraught history, but it probably has one of the region's better designs. Ramps are mostly spaced about a mile apart, with additional roadway crossings every half mile and pedestrian bridges in between those. There's a crossing of some type almost every quarter mile.

Freeways can provide a great improvement in travel speeds, but designers have often been too focused on providing more car access to the freeway than improving the ability for people in all types of traffic to get across freeways or around and between nearby neighborhoods.

Some ramps should be removed, though in most cases the bridges crossing the freeway should be maintained. The bridges could also be reworked to add new freeway BRT stops, like the 46th Street station along Interstate 35W in Minneapolis—rather than removing access, it would change the type of freeway access from automotive to transit. In the long term, that would improve the overall throughput of the freeway system by getting more people into high-capacity vehicles.

Looking the other direction, our region's current pattern of freeway ramp spacing should provide some lessons to transit planners. Even though the primary mode of transportation on the highway is by car, the spacing varies significantly in response to geography and the surrounding development pattern.

In my mind, it doesn't make sense to say that commuter rail should only stop once every 7 miles, as shown in that display board—many parts of the world have "commuter" trains that stop about as often as our Blue Line light-rail service. Transit planners should be more adaptive and do what's right for a particular corridor rather than sticking too close to an often-arbitrary modal definition.

Besides, how can we expect people to switch to using buses and trains more often when it's harder to reach them than it is to get to the nearest highway? These are some of the questions we need to consider as we work to ensure a stable footing for the future of the region.

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