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Megan McArdle: Does maglev make sense?

It’s hard to see how to develop the Northeast Corridor without building more mass transit. Air travel — well, I don’t need to tell you what air travel is like these days. Interstate 95, the main highway between Boston and Washington, is increasingly choked at all hours. The main routes in and out of the major cities barely move at rush hour, and the local roads connecting the megalopolis’s smaller cities to each other have also clotted up. Within the urban core of Manhattan, it is often faster to walk across town than it is to take a taxi.

Forget the ideological arguments about cars versus mass transit, sprawl versus density: These cities are getting to the point where it is lot less physically possible to move more people around without putting in dedicated bus lanes or more rail.

But what kind of rail? A private company is looking to build a magnetic-levitation train from Washington to Baltimore, and as someone who loves trains and technology, I’m naturally tempted to endorse the project just so that I can ride a maglev before I die. Maglevs — which run along a dedicated transit way using high-powered magnets that keep them levitating above the guides, rather than being attached with wheels to a track — have a lot to recommend them over high-speed rail. They are more expensive to build than conventional rail, but their frictionless movement allows higher speeds and much lower maintenance costs.

On the other hand, they also have drawbacks, such as the fact that you can’t run other trains on those tracks. This is one reason maglevs are faster — they don’t share tracks with poky freight and commuter trains. The drawback is that your new infrastructure project only increases your downtown-to-downtown capacity; it doesn’t do anything to enhance intracity or city-to-suburb transport.

To see why this matters, consider one issue facing California’s high-speed rail system: how to get people to the train. People making comparisons between air travel and the promised three-hour Los Angeles-to-San Francisco commute include the time to get to the airport and clear security in their calculations of the time required for an air journey. That makes train travel look competitive.

But, of course, you should also add in the time needed to get to the train station. And in L.A., that time may be longer than it takes to get to an airport, because the sprawling metro area has multiple major airports (Burbank, LAX, Long Beach), allowing people to fly in and out without spending too much time on the dreaded 405. A single high-speed rail station in downtown Los Angeles would divert some trips, but when you add in a long drive, it would be decidedly inferior to air travel for anyone who was planning to be elsewhere in the city. This is markedly different from the Northeast Corridor’s Acela rail service, to which flying is superior only for the relatively small number of people who happen to live near an airport.

If you just add intercity mass transit without increasing the number of people you can move around a city, one of two things happens: Ridership will stay far below expectations, or you’ll dump more people into your overloaded streets, making local congestion worse. This is why there’s a good argument for high-speed rail over maglev — when you’re not running high-speed trains, you can move some commuters point to point.

For that matter, there’s a good argument for not building the maglev at all and instead investing the money in better commuter rail. But that doesn’t get us any closer to the really important goal, which is letting me ride a maglev.

Megan McArdle writes for Bloomberg News.