Lighten up on transit systems

Although it's good to see renewed interest among bidders for the Seattle Monorail Project, there has been little discussion of alternatives to the heavy, expensive monorail designs being proposed. That needs to change.

Imagine a network of nimble, lightweight, inexpensive vehicles gliding above Seattle's roads on slender, unobtrusive guideways, available on demand to safely speed riders above ground-level congestion. This is the promise of Monorail Done Right, but is not what the Seattle Monorail Project is proposing. Instead, current proposal(s) prescribe what amounts to heavy elevated trains using the same basic technology as the 43-year-old Seattle Center monorail. However, Seattle's transit problems have reached a crossroads that recapitulated 1960s technology is ill-suited to unsnarl: a large-scale solution for moving commuters to and from their jobs, off the network of existing surface roads.

The issues have already been studied and solved, with Seattle needing only the vision to implement the solution: Personal Rapid Transit. Dozens of viable PRT systems have been proposed to transit agencies worldwide, many of which cost just one-half to one-third as much as heavy alternatives, and sometimes even less. Why the cost disparity?

One reason is the inherent inefficiency of "heavy monorail" such as that proposed by the Seattle Monorail Project: Each guideway section is in use only for a small portion of its lifetime, when the train is actually on it. Trains simply weigh a lot, whether elevated or on the ground, requiring substantial guideways and (in the case of monorail) large support columns. Lightweight vehicles require a much slimmer guideway. Support columns can be little larger than telephone poles while still supporting the same ridership as "heavy monorail," because the system is in continuous light use rather than in sporadic but heavy use.

Besides lower cost and slimmer guideways, PRT has many other advantages over "heavy" transit alternatives:

Because vehicles wait at stations, there is often no waiting for a ride.

PRT speeds riders directly to their destination, with no need to stop at every station like buses, trains and monorails.

PRT's energy cost to transport riders is much lower -- it's not stopping and restarting a heavy train at every station; it's just moving the passengers plus a lightweight shell around them.

Lower energy use means less pollution.

PRT stations are much smaller than heavy transit alternatives.

Disabled PRT vehicles are easy to move off-line, with minimal service effect.

PRT connectivity increases as the network grows larger and multidirectional: Guideways can have their own interchanges, eliminating the need for vehicle transfers just to change direction.

PRT's distributed nature lowers the risk of potential terrorist activities. Only a few vehicles can be threatened by a single incident, rather than entire trains, making PRT systems unattractive targets and reducing the number of people threatened.

In virtually every case where PRT has been proposed, including Cincinnati, Stockholm, Minneapolis, Wales, the Microsoft campus in Redmond, Seoul, SeaTac, Silicon Valley, and many other locations, PRT has been found to cost less than monorail, light rail and sometimes even buses, while promising equivalent ridership and quicker transit times.

PRT systems have been heavily simulated (you can even download simulation software from at least one vendor) and, in at least three cases, have been prototyped and successfully tested. Some critical work already done by the Seattle Monorail Project, such as rights of way, can even be incorporated into the planning for a PRT network.

So with all these advantages, why isn't PRT everywhere? The answer is that communities can be hesitant to adopt new technologies, but it doesn't have to be that way for a city at the cutting edge of transportation and computing technology. Seattle built a successful "unproven" mass transit system once before, the Seattle Center monorail, which paid for itself within six months. Our city is at a similar tipping point today, with energy costs at unprecedented levels and funds in short supply, yet interest in monorail remains high.

The residents of Seattle want innovative, inexpensive, truly great mass transit, and a system to accomplish this is within reach. Why not build it?

John C. Todd Jr. is a software systems architect/developer and a writer who lives in Seattle.

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