The Virtues of Crowded Transit

Ryan Avent reads a Federal Transit Administration study on that compares emissions and energy use per passenger mile across different transportation modes. Not surprisingly, it shows that transit does better than personal automobiles in both a per-mile and lifecycle (i.e., thinking about the energy that goes into production and deployment) point of view:

But a couple of interesting things stand out. One is that increasing transit ridership has a dramatic effect on average emissions, especially for buses. The reason, of course, is that a lot of carbon is emitted setting up and running a train or a bus, but very little additional carbon is emitted as riders are added. The get the most emission savings out of the technology, then, you want to run transit pretty full. And the other thing that stands out is that, according to research cited by the FTA, the effect that transit has on land-use produces twice the reduction in emissions as the mode shift itself.

What this means is that if you’re interested in reducing the nation’s carbon emissions, you ought to be interested in building new transit. But what it also suggests is that just laying the tracks or buying the buses, and doing nothing else insitutionally, is leaving most of the potential carbon savings from transit on the table. You also need to work to maximize ridership, by eliminating silly automobile subsidies, for instance (like free parking and underpriced roads), or by making your system easier to use (by partnering with Google Transit). And you need to allow transit to shape development around stations, by changing zoning rules and street patterns (as Tysons Corner intends to do), and by facilitating density in other ways (like ensuring that NIMBYism doesn’t stand in the way of quality, dense, developments).

One thing to say about this is that it highlights why it would be a good idea to get our fare-setting policies right. Currently, pretty much every transit agency I’m aware of receives a public subsidy that leaves it dependent on using fare collection as a source of revenue. This is a mistake. The fixed costs of quality transit construction are high, but the marginal costs of carrying additional passengers are very low, and the public goods associated with transit use are higher when more people use transit. Ideally, then, fares on uncrowded bus or rail lines should be very low or even non-existent. Fares should come into play when an at-capacity transit line is in danger of becoming overcrowded. For example, the portion of downtown Washington DC where the Orange and Blue lines run on the same track is, during rush hour, extremely crowded even given the fairly high fare. Under the circumstances, reducing fares would be counterproductive and possibly dangerous. But when crowding isn’t an issue, use should be encouraged through fares that are as low as possible.

And of course much the same principle applies to roads. Roads that are prone to overcrowding ought to have fees associated with them that are designed to bring the congestion under control. And other roads — or the same roads at uncrowded times — ought to be free.