Two floating bridges across Lake Washington connect Seattle with its eastern suburbs. The roadbeds rest on huge pontoons and sway a bit as you drive across them on a windy day.

One is the last gasp of Interstate 90 as it finishes its journey from Boston to the Puget Sound. The other is State Route 520 or “the 520,” as it’s known.

Which bridge to take from where, at what time, using which entrances and exits, has long been a major preoccupation of Seattleites and a frequent icebreaker with strangers. Making the wrong choice can cost you an hour or more sitting in traffic. Everyone has a pet strategy. (“What I like to do is get off at Montlake and then dismantle the car and carry the pieces up to U-Village, where I can reassemble it and proceed up 15th Street. … But you’ve gotta be on the road by 3 a.m. or you’re going to get trapped.”)

All of this changed, though, in December, when the state began collecting tolls on the 520 bridge. It’s not cheap: as much as $5 each way at rush hour. There’s already a price increase in the works for this summer. The I-90 bridge remains free.

Technologically, the system is a marvel. There are no toll booths. Indeed, there is no sign at all that this is a toll road except for actual signs that say so. The toll is collected in myriad ways. You can sign up for an account and get a little coded sticker for your windshield. Or you can wait until they bill you, using your license plate to track you down. Apparently, it works. Unless your commute is between 11 p.m. and 5 a.m., in which case it’s free, you can’t escape.

Except, of course, by taking I-90. That — no surprise — is what has happened. Now the I-90 bridge is more jammed than ever, but if you have $7 to $10 a day to pay for the privilege, you can sail on the 520 at any time.

Economists love this kind of thing. The money raised will be used to rebuild the bridge. Thus this cost will be paid by those who actually use the bridge, in direct proportion to how much they use it, rather than sticking it to the general taxpayer. The market will sort out those who value their time at more than $10 per commute from those who do not and give both drivers what they prefer.

And of course, it’s good for the environment: Some people will reject both the toll and the increased congestion on the free bridge, and use public transit or work from home.

Governments around the world are trying variations on this approach. In London, there’s a daily fee for every car driven into the center of town. In Barcelona, there’s a tunnel that speeds you past the worst congestion, if you’re willing to pay. It’s not a terrible idea. Unlike taxes, these fees are tied to a particular benefit, which makes them easier to swallow. So does the fact that they are voluntary.

In Seattle, since the toll was imposed, traffic on the toll bridge has dropped about 40 percent, while traffic on the free bridge has risen 10 percent. Overall traffic from the east side to and from the city has dropped about 6 percent.

Does this constitute success? That depends on your definition of success. As with the cigarette tax, the more effective a fee is in changing undesired behavior, the less money it brings in. Toll revenue from the 520 bridge is supposed to raise about $1 billion of the $4 billion-plus cost of the new bridge.

But the big problem with the new toll is that it is another small chipping way of our shared life as citizens, and another area where money makes the difference. It used to be that no matter how rich you were, there were some things you could not buy your way out of. Rush-hour congestion was one of them. The law, in its majesty, allowed rich and poor alike to get stuck in traffic. I once heard Steve Ballmer, chief executive of Microsoft and worth many billions of dollars, talking about his strategy for outfoxing the dread 520. (I tried it. It didn’t work.)

As explained by philosopher Michael Walzer, and somewhat more entertainingly by my friend Mickey Kaus, there are two ways to deal with wealth and income inequality (if it bothers you, that is). One is to reduce it, through the tax system. The other is to make money less important. Create national parks, open to everybody. Restore universal military service. And so on.

By this way of thinking, the two bridges side-by-side, one costly to use and one free, constitute a small step backward, toward making money more important. You might say: Wait a minute. What if there already was a toll on both bridges, and it was lifted on one so that people willing to put up with crowds could go across free? That wouldn’t seem iniquitous, would it? But it’s the same thing, really.

And I would say, Great point! Let’s continue this discussion over a drink downtown. And you would look at your watch and say, It’s too late. We’ll never make it across the bridge before dinnertime.

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Michael Kinsley

Michael Kinsley is a Bloomberg View columnist.