Skip to Content
Streetsblog New York City home
Streetsblog New York City home
Log In
Streetsblog

The Diminishing Returns of Highway Building

Today on the Streetsblog Network, David Levinson at the Transportationist presents some interesting explanations about why so much American road building is a poor use of funds:

false

We are not building much new transportation in the US not just because the costs are too high, but because the benefits are too low.

When we were much younger as a nation, say 1956, and growing fast, with relatively poor connectivity, you could do almost anything and it would have a benefit/cost ratio above 1. Very little of the interstate has been reversed. But the productivity of new investments has declined over time...

Diminishing marginal returns to new roads [are] due to diminishing distance reductions as the network is increasingly complete. This is a spatial argument. Imagine you have a network with a 1 mile grid (typical for much of the US). With development of farms, you add roads in between, say at 1/2 mile spacing [see figure above right], this reduces travel costs some, as people don't need to back-track as much, and this might be a significant share of the distance for short trips. At most, you are saving someone 1 mile (1/2 mile at the beginning of the trip, and 1/2 mile at the end of the trip). Now add additional links to diminish spacing to 1/4, This requires twice as many links, but only reduces travel costs by at most 1/4 mile at each end of the trip (1/2 mile total). New links do less and less to reduce distances. Distances, along with speed, determine travel time.

"Peak travel" and induced demand are other reasons Levinson cites for the declining value of spending on roads.

Elsewhere on the Network today: Spacing Toronto celebrates the life of architecture critic Ada Louise Huxtable, whose insights on the built environment helped influence modern planning. Better Institutions says Virginia Governor Bob McDonnell's proposed transportation funding scheme is "the worst transportation funding scheme in modern memory." And Systemic Failure highlights how California transportation agencies are, again, working at cross purposes.

Stay in touch

Sign up for our free newsletter

More from Streetsblog New York City

New Bill Would Block Apps From Deactivating Workers Without Cause

A Brooklyn Council member wants delivery app companies to be more human and less robot.

July 18, 2025

Friday Video: Is Berlin a Great Biking City?

Have recent moves by anti-bike, pro-car legislators ruined the experience in the capital of a unified Germany? Sort of!

July 18, 2025

Eyes on the Street: Meeker Avenue Bike Lane Is a Failure

The Department of Transportation still hasn't finished a critical bike lane under the Brooklyn-Queens Expressway that the agency has been stalling for over four years even after identifying the strip's danger and lack of proper signals.

July 18, 2025

Friday’s Headlines: Cuomo’s Road Rage Edition

Why does Andrew Cuomo drive so recklessly? Plus other news.

July 18, 2025

Fixing Third Ave. Was Once ‘Top of List’ For Eric Adams — But as Mayor He Backed Off

Mayor Adams has delayed a redesign of Brooklyn's Third Avenue despite once saying safety fixes there should be "at the top of our list."

July 17, 2025

Thursday’s Headlines: Jerry Nadler Edition

U.S. Rep. Jerry Nadler faced off with Sean Duffy on Capitol Hill. Plus more news.

July 17, 2025
See all posts