AN EVALUATION OF THE THIRTY FOOT CLEAR ZONE

This study is to evaluate accidents occurring on highway sections built under standards complying with the 30-foot clear zone in order to determine if a safer highway environment has been evident on these sections. The study took place in Illinois. Accident data were in the form of a collision diagram printout for all of the study sections. Data was provided for the routes under study for the period 1 January 1968 to 30 September 1973. Traffic data were extracted from Average Daily Total Traffic maps. A roadway inventory for the study sections was made. Interstate highway sections built to 6:1 safety standards incorporating elements of the 30-foot clear zone have shown lower accident, injury and fatality rates, though not statistically significant. Interstate 70, built almost completely to modified safety standards, showed a better safety record. The before/after studies of safety improvements involving modification of headwalls for 30-foot clearance, placement of guardrail to protect bridge wings, piers, and larger headwalls showed no statistical differences. Recommendations for further study are outlined.

• Corporate Authors:

  University of Illinois, Urbana-Champaign

  Urbana, IL  United States  61801
• Authors:
  • Dotson, V E
• Publication Date: 1974

Media Info

• Features: References;
• Pagination: 41 p.

Subject/Index Terms

• TRT Terms: Average daily traffic; Before and after studies; Crashes; Fatalities; Guardrails; Highway design; Highway safety; Injuries
• Subject Areas: Design; Highways; Safety and Human Factors;

Filing Info

• Accession Number: 00132102
• Record Type: Publication
• Source Agency: National Safety Council Safety Research Info Serv
• Files: TRIS
• Created Date: Oct 29 1977 12:00AM