As a general rule, road pricing isn’t popular. But that’s not because it doesn’t work. The problem is that it works too well, and people don’t like the idea of driving less and paying for roads (that currently have a zero marginal cost).

Here’s a recent study by Robert Bain and Deny Sullivan that looked at just how well it can work. In it, they examine 76 data points from 16 countries, including roads, bridges, tunnels, and cordons (areas).

The question: What happens to demand once the marginal cost of using a road goes from $0 to some cost greater than zero? (As part of this, they also looked at whether the road or bridge in question has viable alternatives.)

The results:

The median traffic reduction was 25%. But the interquartile range was -17% to -44%. This is all very significant. Said differently, the traffic impact in nearly a quarter of the examples was -45% or more. So almost a halving of traffic congestion.

These reductions are obviously a function of the cost of using each road, but regardless, the overarching takeaway remains the same: You may not like or want road pricing, but it totally works.