It’s a classic catch-22; there’s too much traffic in a particular area, so they build more roads. Then traffic increases because now there are more roads to use. This isn’t the only unexpected effect seen in connection with roads and car travel. For one thing, a traffic jam can happen for no apparent reason. You expect it to disappear as drivers realize there isn’t any accident or construction or, really, anything. But it doesn’t disappear. Seen from above, the jam moves, proceeding backward in relation to the direction of traffic. By the time you get to the point where the original jam formed, there’s no jam there — but it still exists elsewhere.
That latter effect is called a “jamiton,” because it seems to be pretty much the same as a “soliton,” which is what physicists call a solitary wave. But what about the former effect? What you really want is not more traffic, but less. There’s a phrase for that, too: “traffic evaporation,” which is NOT what happens when really cheap cars are left outside in the rain for too long (it would be a better story if they did, though).
“Traffic evaporation” is the phenomenon observed by transportation engineers when roads are closed, blocked, or (occasionally) when sufficiently expensive tolls are introduced. Particularly in urban areas where alternative transportation is available, drivers faced with new obstructions to their routes find new ways of getting around, such as buses, trains, rideshares, bikes, and the like. Just like the jamiton, the effect lasts much longer than the apparent cause; some drivers never return to their previous ways, and the traffic simply…evaporates.
Whenever you see cities closing roads or areas to traffic, or, as London did, imposing a toll on driving in a given central area, you can safely assume that in planning meetings, people were talking about “traffic evaporation.” Now what we need is an effective traffic evaporation ray gun — or possibly cheap evaporating cars.
