Bridge rail and approach railing for low-volume roads in Iowa : final report, March 2010.

Details

• Creators:
  Bigelow, Jake ; Hans, Zachary ; Phares, Brent
• Corporate Creators:
  Iowa State University. Institute for Transportation
• Corporate Contributors:
  Iowa. Highway Research Board ; Iowa State University. Center for Transportation Research and Education ; Bridge Engineering Center ; Iowa. Dept. of Transportation
• Subject/TRT Terms:
  • Bridges
  • Bridge railings
  • Guardrails
  • Collisions
  • Low volume roads
  • Bridge approaches Low-volume roads--Iowa
• Publication/ Report Number:
  IHRB Project TR-592;InTrans Project 08-330
• Resource Type:
  Tech Report
• Geographical Coverage:
  Iowa
• Edition:
  Final report
• Corporate Publisher:
  Iowa. Dept. of Transportation
• Abstract:
  Bridge rail and approach guardrails provide safety to drivers by shielding more hazardous objects and redirecting vehicles to the ; roadway. However, guardrail can increase both the initial cost and maintenance cost of a bridge, while adding another object that may ; be struck by vehicles. Most existing low volume road (LVR) bridges in the state of Iowa are currently indicated to not possess bridge ; rail meeting “current acceptable standards”. The primary objective of the research summarized in this report was to provide the nations ; bridge and approach rail state of practice and perform a state wide crash analysis on bridge rails and approach guardrails on LVR ; bridges in Iowa. In support of this objective, the criteria and guidelines used by other bridge owners were investigated, non-standard and ; innovative bridge and approach guardrails for LVR’s were investigated, and descriptive, statistical and economical analyses were ; performed on a state wide crash analysis. ; The state wide crash analysis found the overall number of crashes at/on the more than 17,000+ inventoried and non-inventoried LVR ; bridges in Iowa was fewer than 350 crashes over an eight year period, representing less than 0.1% of the statewide reportable crashes. In ; other words, LVR bridge crashes are fairly rare events. The majority of these crashes occurred on bridges with a traffic volume less than ; 100 vpd and width less than 24 ft. Similarly, the majority of the LVR bridges possess similar characteristics. ; Crash rates were highest for bridges with lower traffic volumes, narrower widths, and negative relative bridge widths (relative bridge ; width is defined as: bridge width minus roadway width). Crash rate did not appear to be effected by bridge length. Statistical analysis ; confirmed that the frequency of vehicle crashes was higher on bridges with a lower width compared to the roadway width. ; The frequency of crashes appeared to not be impacted by weather conditions, but crashes may be over represented at night or in dark ; conditions. Statistical analysis revealed that crashes that occurred on dark roadways were more likely to result in major injury or fatality. ; These findings potentially highlight the importance of appropriate delineation and signing. ; System wide, benefit-cost (B/C) analyses yielded very low B/C ratios for statewide bridge rail improvements. This finding is consistent ; with the aforementioned recommendation to address specific sites where safety concerns exist.
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• Format:
  PDF
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/17869/dot_17869_DS1.pdf
• File Type:
  [PDF - 21.65 MB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:66a978e80343eeadf270d7e1192add1982887fb6acc77c804626ab8eb0944874706b6f6d54e1d17a96e8123daa0f4d682dc4b50a802b81e6c81d0ada25c3c9d7