It’s a common practice for cities to make developers widen a street when they put up a new building. The thinking is that development creates car trips that must be accommodated with more asphalt.
But new research suggests these policies don’t help anyone. The main effect is to increase the cost of building, making housing less affordable.
“As traffic management exercises, many widenings appear unnecessary,” concludes UCLA researcher Michael Manville in a paper published in the Journal of Transport and Land Use [PDF].
Manville looked at how this policy is carried out in Los Angeles. In L.A., all multifamily housing projects (and some other types of construction) are assessed by city traffic engineers to determine whether the developer should widen nearby streets. This is like “blaming Disneyland for increased air travel, and forcing the theme park to expand runways whenever it adds attractions,” he argues.
Manville spoke to developers compelled by the city to pay for various road widenings. The costs varied. In one case, the street widening added an estimated $11,000 to the cost per unit of a multifamily housing development. In another case the figure was $50,000. In another, just $65 per unit. Where the costs of street widenings are substantial, the policy drives up costs for renters and buyers.