CURVE DESIGN AND TESTS ON THE PENNSYLVANIA TURNPIKE

THE PROBLEM OF CURVE, SUPERELEVATION AND SPIRAL DESIGN AND THE INTIMATE RELATION OF REAR END COLLISION SIGHT DISTANCE THERETO IS DISCUSSED. WITH A TOTAL OF 191 CURVES AGGREGATING 50 1/2 MI. IN LENGTH, HAVING RADII VARYING FROM 38,197 TO 955 FT., AND THE NECESSITY OF OFFERING THE MOTORIST UNIFORM AND CONSISTENT OPERATING CONDITIONS AS COMPATIBLE WITH AVAILABLE SIGHT DISTANCE AS POSSIBLE, THE PROBLEM OF THE DESIGNERS MAY BE VISUALIZED. THE SITUATION WAS MET BY ADOPTING SUPERELEVATION BASED ON A STRAIGHT LINE SPEED CURVE UTILIZING LATERAL FRICTION BETWEEN TIRES AND PAVEMENT SURFACE GENERATED BY CENTRIFUGAL FORCE; ARRANGING CURVES IN ORDERLY SEQUENCE SO THAT THE SHARP CURVES WOULD NOT BE ENCOUNTERED SUDDENLY WITHOUT WARNING; BY CONNECTING TANGENTS 6000 FT. OR MORE IN LENGTH WITH THE LIGHTEST FEASIBLE CURVATURE; AND BY THE USE OF SPIRAL EASEMENTS. A THEORY OF THE EFFECT OF BODY ROLL ON CURVE DESIGN IS PRESENTED. THE HIGH SPEED TEST RUNS PERFORMED WITH STOCK MODEL AUTOMOBILES ON THE TURNPIKE ARE DESCRIBED AND THE DETAILED DATA OBTAINED BY THE INSTRUMENTATION IS PRESENTED. WHILE IT IS NOTED THAT AN AVERAGE SPEED OF 103 MPH WITH AN UNBALANCED CENTRIFUGAL RATIO (CORNERING RATIO) OF 0.30 ON A 3 DEG. CURVE AND AN AVERAGE SPEED OF 85 MPH WITH AN UNBALANCED CENTRIFUGAL RATIO OF 0.39 ON A 6 DEG. CURVE WAS ATTAINED, ATTENTION IS SPECIFICALLY DIRECTED TO THE FACT THAT THE TESTS WERE PERFORMED WITH AUTOMOTIVE EQUIPMENT IN PERFECT MECHANICAL CONDITION OPERATED BY A HIGHLY SKILLED DRIVER EXPERIENCED IN HIGH SPEED OPERATION. IT IS POINTED OUT THAT THE SPEEDS AND CENTRIFUGAL RATIOS DEVELOPED SHOULD NOT, THEREFORE, BE CONSIDERED AS SUITABLE FOR THE TRAVELLING PUBLIC. ATTENTION IS DRAWN TO THE FACT THAT A VEHICLE AT HIGH SPEED IS A DYNAMIC MECHANISM OF VARYING STABILITY UNDER THE CONTROL OF AN OPERATOR OF UNCERTAIN SKILL AND THESE VARIABLES PROBABLY BEAR LITTLE RELATION TO TIRE-PAVEMENT FRICTION. BECAUSE OF THESE CONDITIONS THE CONCLUSION IS REACHED BY THE AUTHORS THAT THE RADII OF CURVES, IN THE DESIGN OF NEW HIGHWAYS, SHOULD BE EXPANDED ENOUGH SO THAT AN UNBALANCED CENTRIFUGAL RATIO OF 0.10 IS NOT EXCEEDED WHEN THE DESIGN SPEEDS IS 70 MPH OR MORE. /AUTHOR/

  • Supplemental Notes:
    • Vol 20, pp 429 - 454, 13 FIG, 11 TAB
  • Authors:
    • STONEX, K A
    • Noble, C M
    • Moyer, R A
  • Discussers:
    • Barnett, J
  • Publication Date: 1941

Media Info

  • Monograph Title: Proceedings of the Twentieth Annual Meeting of the Highway Research Board Held at Washington, D.C. December 3-6, 1940
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00203540
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Aug 15 1971 12:00AM