The Antiplanner’s Law of Rail Transit

I often hear people say things like, “Light rail might make sense in Europe, but it doesn’t make sense here because our city isn’t dense enough.” To which I respond, “Light rail doesn’t make sense in Europe either.”

In fact, based on the numbers in the post on moderate-capacity transit, we can derive the following Antiplanner’s Law of Rail Transit:

By the time a city is dense enough to justify rail transit, it is too dense for light-rail transit.

The proof of this is simple. We know that three-car light-rail trains can move fewer than 250,000 passenger miles per hour, while subways and exclusive bus lanes can move more than 1.7 million passenger miles per hour. Thus, if you need low-capacity transit, use small buses. If you need moderate-capacity transit, use big buses. If you need high-capacity transit, use lots of big buses and some exclusive bus lanes. Only if you need really high-capacity transit and have too much congestion for buses to operate effectively would you turn to subways or other forms of heavy rail.

Light rail does not fit in the efficient transit continuum anywhere except in the minds of pork-barreling politicians and rent-seeking rail contractors.

Now my loyal opponent, Michael Setty (msetty), responded to the moderate-capacity transit post on his own blog, PublicTransit.US. His response makes a few mistakes.

“The capacity of a particular form of transportation technology has relatively little to do with speed,” he says, “but everything to do with the minimum frequency that trains can operate safely and reliably past a given point.” That is silly. Speed is just as important as frequency. If one mode goes three times faster than another mode, then all else being equal it has three times the capacity.

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By Mr. Setty’s criteria, since more people walked past a point than drive, the bridge would do more work if devoted entirely to pedestrians than to autos. In fact, because the autos can go 60 miles per hour and pedestrians only 3, the bridge does far more work serving autos.

Mr. Setty accepts transit agency predictions that a light-rail line across the Columbia River “would provide about 25% of the peak hour capacity across the river, commensurate with LRT’s share of the overall project cost.” In other words, it would carry about one freeway lane’s worth of traffic. Even if true, for the non-peak hours, it would carry far less than a freeway lane’s worth of traffic. Portland’s light-rail lines carry about 22 percent of a Portland freeway lane.

That’s why the real solution to many of our congestion problems is not light rail or exclusive bus lanes but variable-priced toll lanes. The pricing would insure that the toll lanes would never become congested, so buses could use the lanes at any time without facing slowdowns. The pricing would also insure that the lanes receive considerable use during non-peak hours, whereas the expensive light-rail line would be virtually empty most of the day (and completely empty at night, when most cities stop operating their rail lines).

Mr. Setty also raises the question of where all the traffic will go. “The Antiplanner is nominally correct that a freeway lane can carry around 600 buses per hour,” he says, “however, this rate is actually achieved only in New York City and then only because the Port Authority Bus Terminal has nearly 300 bus bays that can absorb such volumes.” But that is exactly my point: it takes New York City densities to justify an exclusive bus lane. But if buses can serve those densities, why do we need light rail?

Buses have two advantages over rail. First, they can disperse to many different destinations. When crossing the Columbia River they can use a high-occupancy/toll lane. Then some buses can go to Vancouver, some to Hazel Dell, and some to Battleground. Light rail would be limited to one or, possibly, two high-cost fixed routes.

The second advantage is that buses can share the road, and therefore the cost of the road, with autos and trucks. This means the road can be used by others when buses aren’t using it. Meanwhile, expensive rail lines sit idle most of the time, either because there is no demand to run frequent trains or because frequencies can be no greater than the safe operating limits of the system — which, as Mr. Setty admits, is about twenty trains per hour for most light rail.

We must also never forget the biggest advantage highways have over rail: Not only do they cost less, but all or almost all the costs are paid for by users. So even if light-rail’s share of costs was commensurate with its use (which it isn’t), light-rail riders would be heavily subsidized by auto drivers, while the drivers would be pretty much paying their own way.

Is there a reason why light-rail riders deserve such a subsidy? Especially when equal or better service can be provided by buses at a much lower cost? Of course not. If someone is so snobbish that they will only ride a train, and not a public transit bus, then let them drive in their Mercedes. We don’t need, and really can’t afford, to subsidize snobs.