摘要: |
The highway system has a pervasive presence in U.S. society. Whether driving, biking, or traveling by bus, many Americans use the nations roads every day in their personal, professional, family, and social activities. The 4-million-mile highway system is the backbone of the U.S. economy, carrying 65 percent of the nations $15 trillion in freight traffic and 88 percent of all noncommercial person miles traveled. The highway network also provides passenger and freight links to all other modes of transportation. U.S. highway facilities have been in constant use for decades, often exceeding their original design life and traffic volumes. As a result, the system is deteriorating and heavily congested. Moreover, deaths and injuries from highway crashes constitute a major public health concern. |