HSIS Summary Report
Matthew W. Knuiman, Forrest M. Council, and Donald W. Reinfurt
Aug-93
This study examined the effect of median width on the frequency and severity of crashes on homogeneous highway sections with a traversable (nonbarrier) median. Crash data from 982 highway sections in Utah and 2,481 highway sections in Illinois were used in the analyses. Log-linear models were used to assess the effects of median width and other roadway variables on the crash rate. The total crash rate appears to decline steadily with increasing median width from 0 to 33.5 m (0 to 110 ft). For Utah it declines by a factor of six, and for Illinois, it declines by a factor of 13. Over this range of median width, the rates of serious injury, all injury, and property-damage-only crashes also decline by up to a factor of 15. However, when constructing new highways, medians need to be at least 9.1 m (30 ft) wide to have a positive safety effect. Additional data will be needed to determine the median width at which a median barrier should be used.
The Association of Median Width and Highway Accident Rate
Median width
Crash rates
Log-linear models
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.
