0-7183: Develop Crash Modification Factors for Super 2 Highways [Brief]

Details

• Creators:
  Brewer, Marcus A. ; Geedipally, Srinivas R. ; Speed, John ; Fitzpatrick, Kay ; Das, Subasish
• Corporate Creators:
  Texas A&M University System. Texas Transportation Institute
• Corporate Contributors:
  Texas Department of Transportation. Research and Technology Implementation Office
• Subject/TRT Terms:
  Crash Analysis Crash Characteristics Crash Modification Factors Data Files Passing Lanes Rural Highways Two Lane Highways
• Resource Type:
  Brief
• Geographical Coverage:
  United States;Texas
• Edition:
  Project Summary Report
• Contracting Officer:
  Dassi, Martin
• Corporate Publisher:
  Texas. Department of Transportation
• Abstract:
  Super 2 highways have been used across Texas for over 20 years, providing operational and safety benefits to rural two-lane highways at a lower cost than widening such facilities to four lanes. More Super 2 highways are planned as the demand increases on the state highway system. Previous research has provided insights on Super 2 safety, but updated crash modification factors (CMFs) based on a rigorous analysis of recent crash data would provide additional support for installing Super 2 corridors throughout the state and complement existing guidance. This project investigated the crash history of existing Super 2 highway corridors in Texas before and after installation, compared to similar two-lane highways without Super 2 passing lanes. Researchers developed a comprehensive dataset of 67 Super 2 corridors for analysis and identification of relationships between crashes and other characteristics. Researchers also developed a database of 165 reference segments (i.e., two-lane highway segments without passing lanes) for crash history comparisons with Super 2 corridors. An empirical Bayes before-after analysis of available crash data revealed that Super 2 highways reduced total crashes by 21 percent compared to traditional rural two-lane highways. This result was statistically significant, with a 95 percent confidence interval between 16 and 26 percent for total crashes. Similar results were observed for fatal-injury (KABC) and property damage only (PDO) crashes; Super 2 highways reduced KABC and PDO crashes by 16 and 23 percent, respectively. This research provides guidance on the selection and use of appropriate CMFs for construction projects that include Super 2 passing lanes, along with suggestions for updates to the TxDOT Roadway Design Manual and recommendations for future research.
• Format:
  PDF
• Funding:
  0-7183
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:061455bc3d957e98c03e5ade7900baabebc425869e747e8b71316e7eeb5d9a5d516410366048cdee1f3a30e9b8faa3896754db535f13228a3e5347305e2e7569
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/86027/dot_86027_DS1.pdf
• File Type:
  [PDF - 320.27 KB ]