This research was undertaken following testimony concerning highway safety and, more specifically, narrow bridge problems, at hearings of the Subcommittee on Investigation and Review, Committee on Public Works, U.S. House of Representatives. The objectives of the study were to define the narrow bridge problem, appraise the effectiveness of corrective measures, and develop guidelines for corrective treatment at various bridge sites. A nationwide narrow bridge survey conducted as part of the project indicated that there may be as many as 60,000 highway bridges in the United States that are deficient in width. Field studies were conducted at 25 selected bridge sites in 7 states. Driver performance in terms of speed and lateral position was determined for each site. Modifications of signing and delineation were made at several sites. Before-and-after accident experience was available for one section of road where corrective treatments had been applied to several narrow bridges. On the basis of the data collection and analysis, and the experience of the researchers, the BSI was developed as the combination of 10 individual bridge site rating factors. Its development is considered the most significant accomplishment of the research effort. For most bridges, it can be used to determine a reasonable estimate of the relative degree of hazard of the site in comparison with other sites. (Author/publisher)
Samenvatting