Diminishing Returns From Highway Investments Part I: We knew 20 years ago that highway investments were not providing sensible economic returns when (in 2006) the Brookings Institution found that every dollar invested in new lane miles only bring about 11 cents in congestion benefits: https://www.brookings.edu/articles/the-effect-of-government-highway-spending-on-road-users-congestion-costs/
The Effect of Government Highway Spending on Road Users’ Congestion Costs

AEI Joint Center paper by Clifford Winston (May 2006)

Brookings