THE RELATIONSHIP BETWEEN ACCIDENT DATA AND THE WIDTH OF GRAVEL SHOULDERS IN OREGON

THE EFFECT OF WIDTH OF GRAVELED SHOULDERS ON NONINTER- SECTIONAL ACCIDENTS WAS STUDIED. IT WAS FOUND THAT ACCIDENT FREQUENCY WAS NOT RELATED TO SHOULDER WIDTH FOR THE LOWER ADT HIGHWAYS (ADT LESS THAN 3600). THIS WAS SUPPORTED BY THE FACT THAT ACCIDENT OCCURRENCE DID NOT SEEM TO BE RELATED TO OTHER CONTROLLED ROADWAY FEATURES: COMMERCIAL AND RESIDENTIAL DRIVEWAYS, LANE WIDTH, CURVES, TERRAIN, OR SIGHT RESTRICTIONS. THERE WAS A TENDENCY FOR ACCIDENT REDUCTION AS SHOULDER WIDTH INCREASED IN THE HIGHER ADT RANGES. THIS WAS STATISTICALLY RELIABLE FOR TOTAL ACCIDENTS AND PROPERTY DAMAGE ACCIDENTS IN THE 3600 TO 5500 ADT RANGE. THIS INVERSE RELATIONSHIP CONCURS WITH THE IMPLICIT ASSUMPTIONS OF HIGHWAY DESIGNERS WHO FELT THAT CONGESTION ALLEVIATION ON HIGHER ADT 2-LANE ROADWAYS IS NECESSARY. IN PRACTICE, SHOULDERS ARE WIDENED. FROM THE RESULTS IT APPEARS REASONABLE TO SUSPECT THAT SHOULDER IMPROVEMENTS ACTUALLY HELP IN THIS VOLUME RANGE ON 2-LANE RURAL TANGENTS. SPEED CHECKS WERE AVAILABLE FOR MANY SECTIONS IN THE 3600 TO 5500 ADT RANGE AND THE 5600 TO 7500 ADT RANGE. ANALYSIS OF THE SPEED DATA AS A FUNCTION OF SHOULDER WIDTH INDICATED THAT NO SIGNIFICANT RELATIONSHIP EXISTED BETWEEN SHOULDER WIDTH AND SPEED IN THE 3600 TO 5500 ADT RANGE; WHEREAS A HIGHLY POSITIVE RELATIONSHIP EMERGED BETWEEN SPEED AND SHOULDER WIDTH IN THE 5600 TO 7500 ADT RANGE. THE RESULTS MIGHT HAVE ACCOUNTED FOR THE INSIGNIFICANT RELATIONSHIP BETWEEN SHOULDER WIDTH AND ACCIDENTS. IT APPEARED THAT THE CONTRIBUTION OF SHOULDER WIDTH TO ACCIDENT OCCURRENCE TAKEN BY ITSELF WAS GENERALLY SLIGHT ON THE LOWER VOLUME ROADS (ADT LESS THAN 3600). ON HIGHER VOLUME ROADS (3600 TO 7500 ADT), WIDE SHOULDERS TEND TO REDUCE ACCIDENTS, ESPECIALLY PROPERTY DAMAGE AND TOTAL ACCIDENTS. HOWEVER, WHEN THERE WAS A SIGNIFICANT INCREASE IN VEHICLE SPEED WITH WIDE SHOULDERS AS WAS FOUND IN THE 5600 TO 7500 ADT RANGE, THIS TENDENCY FOR A REDUCTION IN ACCIDENTS WITH WIDE SHOULDERS FELL SHORT OF STATISTICAL SIGNIFICANCE. THE POSSIBILITY ARISES THAT PERSONAL INJURY ACCIDENTS WERE AFFECTED BY SHOULDER WIDTH IN A DIFFERENT WAY THAN WAS THE CASE FOR PROPERTY DAMAGE ACCIDENTS. THE CAUSE OF THIS DISCREPANCY IS UNKNOWN UNLESS PAVED SHOULDERS ACCOUNT FOR IT. /AUTHOR/

  • Supplemental Notes:
    • Vol 35, pp 558-576, 7 FIG, 5 TAB, 7 REF, APPS
  • Authors:
    • Head, J A
    • Kaestner, N F
  • Publication Date: 1956

Media Info

  • Monograph Title: Proceedings of the Thirty-Fifth Annual Meeting of the Highway Research Board, Washington, D.C., January 17-20, 1956
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00221357
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Aug 15 1971 12:00AM