Abstract
This article demonstrates the feasibility of exploiting insurance claims data to estimate the marginal benefits to society of highway infrastructure improvements. We construct a unique database linking claims expenditures for a major auto insurer in Michigan to infrastructure investments at 62 intersections in the City of Detroit, and conclude that the addition of a left-turn lane, or left-turn phase in the signal, decreases the insurer's average monthly claims costs at a representative intersection by $944 or $1,062, respectively. The evidence also indicates that these cost savings are a result of reductions in accident severity, rather than being a consequence of fewer accidents. (Author/publisher)