two decades: the U.S. population is predicted to grow by 24 percent by 2030 (Energy Information Administration 2007, Table A2); vehicle miles traveled (VMT) is projected to increase by 60 percent by 2030; truck VMT is projected to increase by 75 percent in the same period (Energy Information Administration 2007, Table 7);2 and truckloads are predicted to increase by 80 percent, to nearly 23 billion tons, by 2035 (FHWA 2007, Table 2-1). This expected growth calls for better system operation and more rapid renewal of in-place infrastructure to optimize the use of existing capacity and improve travel time reliability. There will be a need for additional highway capacity in selected locations to move motorists and freight, as well as additional capacity in public transit, freight rail, and waterborne transportation. One estimate indicates that an additional 173,000 lane miles of Interstate highway will be needed by 2035 just to maintain the current level of highway performance (PB Consult et al. 2007). This estimate, which assumes high levels of investment in transit and passenger rail during the period, implies adding more than 5,700 lane miles of Interstate highway annually for the next 30 years—nearly comparable with the rate of expansion during the Interstate construction years. About half of the forecast need consists of expansion of existing Interstates, and half consists of upgrades of NHS segments to Interstate standards. Any capacity enhancements will have to be performance driven and outcome based while integrating environmental, economic, and community requirements.

Growth in highway usage has safety implications as well. Some 43,000 deaths and millions of injuries occur on the nation’s roads every year, and motor vehicle crashes remain the leading cause of death for those between the ages of 5 and 34 (CDC 2007). Beyond the personal toll, highway crashes are estimated to cost the nation $230 billion annually (Blincoe et al. 2002).3 Despite significant improvements in recent decades,4 several


More recent data show VMT falling; for example, VMT in March 2008 was 4.3 percent lower than that in March 2007 (cf. FHWA 2008b). The long-term impact on VMT and VMT projections is not yet clear.


A study sponsored by the American Automobile Association found that fatal and injury crashes cost $162.2 billion in 85 urban areas in 2005, nearly 2.5 times more than the estimated cost of congestion in those areas (Cambridge Systematics and Meyer 2008).


Between 1970 and 2003, the U.S. highway fatality rate—in terms of fatalities per 100 million VMT—declined by 80 percent (Seiffert 2005). If crash rates were the same now as they were in 1966, the annual number of highway fatalities would be 150,000. Improvements are attributable

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