New York City Mayor Bloomberg announced a proposal for congestion pricing in Lower Manhattan. The system would add an $8 toll to the existing tolls for bridges and tunnels into the city, using cameras that can record the license plate of cars. The idea is modeled upon a successful congestion pricing plan in London introduced by Mayor Ken Livingstone.

This is a great idea that uses modified market incentives to discourage driving, while raising money for road maintenance. It shifts costs from general taxpayers to drivers. The question isn't why New York City and London are doing this, but why other cities around the world aren't.

The typical objections are:

• This is an attack on drivers, and thus politically unviable in cities dominated by driving.
• This makes sense if there is mass transit, but most cities don't have enough mass transit.
• Damn liberals and their freaking taxes and big government!
• Tolls are inconvenient or intrusive.

These reasons are actually closely related, as becomes clear when the idea is examined. It's true that congestion pricing affects drivers. But the flip side of this is that congestion pricing raises revenue for roads. This isn't a raise in taxes but a shift in taxes from the general population to the people who actually put a strain on the road network. That means that there is more room in the general budget for other projects, or for a drop in taxes if people decide that's a better policy. Congestion tolls are an avoidable tax, because people always have the option to use mass transit. Tolls also direct government taxation at a smaller group of people, and acknowledge the usefulness of markets, making them superior to general taxes and policies based on mandates rather than incentives. Those opposed to a high degree of regulation should be happy to support an alternative that reduces regulation. Modern tolls can avoid slowing down traffic by using cameras to identify vehicles, sending a bill every so often to the owner of each vehicle. These cameras are no more intrusive than the transportation cameras that are already in use in most cities.

That leaves the question as to how much public transportation is required for congestion pricing to work. Cities with poor public transportation provide few options for commuters, most of whom will have no choice but to pay the toll, move, or change jobs. Most will simply pay. But that's not a bad thing. Even in a city with no public transportation, tolls represent a fairer way to pay for road maintenance. They encourage people to move closer within the toll boundary, or to get a job closer to their home, completely outside the toll boundary. In either case, transportation is made more efficiently. As for bringing better public transportation, by shifting road costs to tolls, more money is available in the budget of cities to improve mass transit.

Only if the toll is so onerous that it impacts the overall economy of a city is it a bad idea. So setting the level of the toll is important. The toll should encourage more efficient use of roads and increased use of mass transit without being an economic burden. One way to ensure this is to exempt certain vehicles from the toll, such as trucks delivering freight to and from major ports. Another is to start with a relatively low toll, measure the effect, and then modify the toll based upon the results on traffic and economic development.

Here's what I envision for Seattle. The city of Seattle is geographically constrained, particularly on the north, west, and east. While the worst traffic areas might be in the downtown core, it's actually easier to set tolling cameras based on geographic features. The Lake Washington Ship Canal is crossed at only six points--I-5, SR 99, Montlake, University, Fremont, and Ballard. The two floating bridges are the only points in from the east. Most of the west side of the city is on Elliott Bay, except for West Seattle across the Duwamish. There are two bridges that cross here--the West Seattle Bridge and the bridge for SR 99/509. Boeing Field takes up most of the rest of the city to I-5, and toll cameras at the correct points on East Marginal Way and Airport Way, and northbound I-5, complete the tolling system on that side of the city. The southeast part of the city is a little more difficult, but a close look at the map shows that putting in four cameras along the four major roads that cross at or near Henderson Street north of the Rainier Beach neighborhood is sufficient to cover every route into the city.

Seventeen cameras. WSDOT already has cameras in the right spots north and southbound on I-5, on I-90, on 520, and several close to other locations, and it would not be difficult to upgrade these cameras for tolling purposes and add fourteen more in the other locations. Beyond that, all that is needed is an administrative system to mail bills and collect tolls.

Set the toll to start at $1.50, which matches the one-zone peak fare for Metro and Sound Transit buses. Reduce or eliminate the tolls for off-peak and low-congestion hours. Incorporate the existing local MVET (motor vehicle excise tax) fees into this toll, to simplify local taxes. When the light rail trains open, make sure that the toll is at least as high as the light rail fare. Direct 50% to road maintenance and 50% to transit.

If the early system is successful, add an additional dynamic toll above the flat congestion price rate that rises and falls with congestion on each major regional highway, and signs in key locations that advertise the current price. This way, motorists can choose the cheaper and less congested routes based on live information about traffic. This increases efficiency of the roads while raising even more revenue for road and transit projects.

Finally, as state and federal carbon mandates are introduced, adjust the system to ensure compliance with those mandates. If there's a carbon tax, it will be possible to distribute the tax according to road use, if that's allowed. If there's a carbon cap and trade, the tolls can be used to reduce the city's use of greenhouse gases and possibly generate carbon credits that can offset the additional tolls. During economic downturns, the tolls could be adjusted downward temporarily to help ease the impact on lower-income commuters and encourage short-term economic growth.

When I briefly outlined this idea over at the Slog, I was told that this was tantamount to banning cars from the city, and that I was better off voting for Kucinich and Nader in 2008. To the contrary, I think this is an achievable and moderate step that could be sold politically, while also actually making a difference for the city of Seattle.