Performance assessment of road barriers in Indiana.

Details

• Creators:
  Zou, Yaotian ; Tarko, Andrew P.
• Corporate Creators:
  Purdue University. Joint Transportation Research Program
• Corporate Contributors:
  Indiana Department of Transportation ; United States. Federal Highway Administration
• Subject/TRT Terms:
  • Median barriers
  • Barriers (Roads)
  • Guardrails
  • road barriers
  • median barriers
  • roadside barriers
  • safety impact
• Publication/ Report Number:
  FHWA/IN/JTRP-2016/12
• Resource Type:
  Tech Report
• Geographical Coverage:
  Indiana
• Corporate Publisher:
  Purdue University. Joint Transportation Research Program
• Abstract:
  Road barriers have been used as an effective countermeasure to prevent exposure of errant vehicles to both vehicles travelling in the opposite direction ; and to roadside hazards. The objective of this study was to evaluate the in-service safety performance of three types of road barriers (concrete barriers, ; steel W-beam guardrails, and high-tension cable barriers) in Indiana using cross-sectional analysis based on crash data. The quantitative evaluation was ; comprised of three components: 1) the effect of the road, barrier scenarios, and traffic on the barrier-relevant (BR) crash frequency, 2) the effect of the ; road and the barrier scenarios on the BR harmful events, and 3) the effect of the BR events and other conditions on the injury outcomes. ; The introduction of the BR harmful events linked the crash onset with its outcome. The three developed statistical models were connected through their ; inputs-outputs and followed the sequence of various BR events during the BR crash. This improvement allowed a more comprehensive and insightful ; analysis of the barriers’ safety effects and a more efficient use of data. The injury outcomes were estimated for all the individuals in a crash rather than for ; the most severe outcome of a crash. Further improvement of the cost estimates was accomplished by utilizing hospital data. ; For median barriers, this study found that the total number of BR crashes was higher with the use of median barriers, mostly due to the introduction of ; collisions with barriers and an increase in the collisions after redirecting vehicles back to traffic. These undesirable effects of barriers were surpassed by ; the positive results of reducing hazardous events such as cross-median crashes, rollover events, and collisions with roadside hazards, which substantially ; reduced the number of severe injuries and fatalities. ; The average (unit) crash costs were estimated for roads without barriers and for roads with various barrier scenarios. The crash costs were reduced by ; 50% where cable barriers were in medians wider than 50 feet and where concrete barriers or guardrails were in medians less than or equal to 50 feet ; wide. Roadside barriers (guardrails) reduced the unit crash costs by 20% to 30%. ; Median cable barriers were found to be the most effective among all the studied barriers due to the smallest increase in the crash frequency and least ; severe injuries in barrier-relevant crashes. A cable barrier’s offset to the travelled way was also investigated in this study. When considering vehicles ; moving in one direction, the nearside cable barriers installed at an offset less than or equal to 30 feet performed better than far-side cable barriers with a ; larger offsets thanks to the better protection they provide for vehicles against rollovers in the median and impact with the median drain. Consequently, ; the biggest safety benefit can be expected where cables barriers are installed in the median at both edges. ; The results were implemented through a set of crash modification factors and unit crash costs estimated for 51 road-barrier scenarios. An implementation ; procedure is provided to quantify the crash costs and the safety benefits for these scenarios.
  More +
• Format:
  PDF
• Funding:
  SPR-3705
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/31564/dot_31564_DS1.pdf
• File Type:
  [PDF - 3.88 MB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha256:5d893b2d6c44cfd5a63557abf0237be3e268cd8210d8435449c76b974d9c128f