One More Lane
You run the freeway for 20 years. Every lane you add opens to cheers and fills right back up. Somewhere on this screen is the thing that actually works.
The Lane Always Fills
Duranton and Turner found that driving on U.S. interstates rises almost one for one with lane miles. Andrew Sachs, PTMP, on why the answer runs through price and the parking space.
Game model, simplified and sped up: one year passes every 3.5 seconds. Traffic settles toward the level where the next trip is barely worth taking, so added lanes fill at close to one for one (elasticity about 0.97 here; Duranton and Turner estimate 1.04), with a 2.2-year half-life. Speeds follow the article’s curve, 65 / (1 + 1.32x⁶). A toll or a parking price raises the cost of each trip, and free parking lets households add cars faster. Lane costs, toll revenue, the strike timing and the mayor are illustrative.