FLAT EMBANKMENT SLOPE VERSUS GUARDRAIL: COMPARATIVE ECONOMY AND SAFETY

THE THESIS THAT THE AESTHETICALLY DESIGNED HIGHWAY IS USUALLY THE MOST ECONOMICAL HIGHWAY TO CONSTRUCT AND MAINTAIN AND IS INHERENTLY SAFE IS EXAMINED WITH RESPECT TO ONE IMPORTANT DESIGN COMPONENT HAVING SUBSTANTIAL AESTHETIC SIGNIFICANCE: ROADSIDE DESIGN OVER EMBANKMENTS. THE EQUAL-COST OR ECONOMIC BREAK-EVEN HEIGHT OF EMBANKMENT IS DETERMINED FOR A RANGE OF UNIT CONSTRUCTION AND MAINTENANCE COSTS AND BASIC TYPES OF EMBANKMENT PROFILES. THE RELATIONSHIP BETWEEN ECONOMIC BREAK-EVEN HEIGHT AND SAFETY BREAK-EVEN HEIGHT - THE HEIGHT AT WHICH AN UNPROTECTED SIDE SLOPE IS EQUAL IN ACCIDENT SEVERITY TO COLLISION WITH GUARDRAIL - IS EXAMINED. ECONOMIC BREAK-EVEN HEIGHT VARIES CONSIDERABLY WITH UNIT COSTS AND EMBANKMENT PROFILE AND IS GENERALLY WELL BELOW THE SAFETY BREAK-EVEN HEIGHT; THUS THERE IS A WIDE SPAN IN FILL HEIGHT OVER WHICH GUARDRAIL INSTALLATION IS CHEAPER THAN SLOPE FLATTENING, BUT DESIGN WITH FLATTENED SLOPE IS SAFER. ECONOMIC BREAK-EVEN HEIGHTS FOR EMBANKMENTS OF SMOOTHLY VARYING HEIGHT ARE SIGNIFICANTLY GREATER THAN THOSE FOR CONSTANT-HEIGHT EMBANKMENTS. RIGHT-OF-WAY COST IN RURAL AREAS IS LIKELY TO HAVE LITTLE EFFECT ON BREAK-EVEN HEIGHT, WHILE CULVERT COST CAN CONSIDERABLY REDUCE IT. THE RESULTS OF THIS STUDY TOGETHER WITH WHAT APPEARS TO BE AN EXCESSIVE AMOUNT OF ROADSIDE GUARDRAIL OVER EMBANKMENTS ON RURAL HIGHWAYS AND AT INTERCHANGES INDICATE THAT MANY HIGHWAY DESIGNERS SUBSTANTIALLY UNDERESTIMATE THE ECONOMIC BREAK-EVEN HEIGHT FOR FLATTENED SIDESLOPES. /AUTHOR/

Media Info

  • Media Type: Print
  • Features: Figures; References; Tables;
  • Pagination: pp 10-24
  • Monograph Title: Geometric design, protective barrier systems, luminaire supports
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00203474
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Sep 21 1970 12:00AM