Research Shows More Roads = More Driving

A new study, Road Capacity as a Fundamental Determinant of Vehicle Travel, published by  the University of California Institute of Transportation Studies, indicates that roadway supply is a key factor affecting the amount that people drive in a community. It uses U.S. national data to analyze factors that affect vehicle travel. It finds that road capacity has a larger effect on per capita VMT than factors traditionally considered, such as income and fuel prices. This provides aggregate evidence that roadway expansions induce additional vehicle travel, particularly over the long run.

Road supply does not just affect traffic speeds and automobile accessibility but also impacts pedestrian connectivity, land development, transit service feasibility, plus household residential and employment location decisions. The researchers point out that per capita vehicle travel peaked early in the Twenty First Century so road capacity rather than income or fuel price has emerged as the fundamental factor affecting vehicle travel. 

The study concludes that achieving VMT reduction targets are likely to require road capacity reductions.