Safety Evaluation of Curve Warning Speed Signs

This report presents a review of a research effort to evaluate the safety implications of advisory speeds at horizontal curve locations on Oregon rural two-lane highways. The primary goals of this research effort were to characterize driving operations at rural two-lane highway curve locations where advisory speed signs were present, and to determine to what extent these signs play a role in enhancing safety. Placement of advisory speed signs at horizontal curve locations in the State of Oregon is a practice aided by unique and specific state-level policies and, as such, may vary from nationally accepted procedures. Speed data were collected at 16 sites and compliance with advisory speed signs determined. An evaluation of site crash data and how advisory speed relates to historic crash information is included along with a statistical model that identifies critical variables that are associated with the posted speed and how they ultimately relate to the expected crash frequency. The research team developed a statistically based advisory speed model that assesses predicted crash outcomes based on a combination of geometric design, operations, and signage. The resulting advisory speed models were then contrasted to the expected advisory speeds based on the Oregon Policy as well as the 2009 Manual on Uniform Traffic Control Devices (MUTCD) thresholds. They determined that the safety-based model actually predicted advisory speeds that are not as conservative as those recommended using the ball-bank thresholds in the 2009 MUTCD or those identified using the thresholds Oregon has been using. Just prior to publication of this report, the Oregon Traffic Control Devices Committee (OTCDC) decided to adopt the 2009 MUTCD without making an exception to advisory speed posting guidelines. The Oregon Department of Transportation (ODOT) has begun to transition to the 2009 MUTCD advisory speed posting criteria. Actual adoption of the 2009 MUTCD is expected to occur in August 2011.

Language

  • English

Media Info

  • Media Type: Web
  • Edition: Final Report
  • Features: Appendices; Figures; Maps; Photos; References; Tables;
  • Pagination: 151p

Subject/Index Terms

Filing Info

  • Accession Number: 01346513
  • Record Type: Publication
  • Report/Paper Numbers: FHWA-OR-RD 11-14, OTREC-RR -11-18
  • Contract Numbers: SPR 685
  • Files: UTC, NTL, TRIS, ATRI, USDOT, STATEDOT
  • Created Date: Aug 4 2011 9:34AM