HSIS Summary Report
Forrest M. Council and J. Richard Stewart
Nov-99
As congestion on two-lane rural roads increases, there is increasing interest in conversion to a four-lane divided facility within the same corridor. The authors have attempted to estimate the benefits of such conversions by developing cross-sectional models producing crash rates for typical sections of two- and four-lane roadways in California, Michigan, North Carolina, and Washington. Predicted crash reductions for conversion from most typical two- to four-lane divided sections ranged from 40-60 percent. The reduction due to conversion to a four-lane undivided configuration is much less well defined, ranging from a 20 percent reduction to a slight increase. Future research needs include (a) verification of the undivided four-lane results, (b) additional information on the effects of driveways, (c) estimates for higher levels of two-lane average daily traffic, (d) expansion of the outcome variable to include crash severity, and (e) verification of all results by before-and-after studies of actual conversions.
Safety Effects of the Conversion of Rural Two-Lane Roadways to Four-Lane Roadways
Two-lane roads
Four-lane roads
Cross-sectional models
Crash rates
HSIS
HSIS Summary Reports are two to eight pages in length and include a brief description of the issue addressed, data used, methodology applied, significant results, and practical implications.
A variety of research studies have been performed using data from HSIS. Many of the final reports prepared are now available electronically.
Research reports are often summarized in executive summaries, technical briefs, or other abbreviated formats. Included here are those road safety summaries that involved research using HSIS data.
In addition to conducting research, HSIS resources are also used to develop products that can be used by practitioners in the analysis of safety problems.
HSIS data are sometimes used in research studies that result in other types of finished products, such as dissertations, theses, and conference proceedings.