RELATIONS BETWEEN CURVATURE AND SPEED

IN ORDER TO DESIGN THE CURVED PORTIONS OF HIGHWAYS PROPERLY IT IS NECESSARY TO STUDY THE BEHAVIOR OF CARS ON CURVES. BOTH ON STRAIGHT AND CURVED HIGHWAYS THE BEHAVIOR IS DETERMINED LARGELY BY THE SIDE FORCES ACTING AGAINST THE WHEELS AND BODY. SIDE FORCES ARE DIFFICULT TO MEASURE ON A STRAIGHT HIGHWAY AS THEY ARE VARIABLE, BEING CAUSED BY ROAD CAMBER AND SIDE WIND. ON A CURVE, THE PRINCIPLE SIDE FORCE IS DUE TO THE CENTRIFUGAL ACTION WHICH CAN BE CONTROLLED BY DRIVING THE CAR ON A CIRCLE OF MEASURED RADIUS AT CONSTANT SPEED. THIS FORMS THE BASIS FOR TESTS MADE AT THE GENERAL MOTORS PROVING GROUND ON A LARGE NUMBER OF CARS. TEST METHODS ARE DESCRIBED AND TYPICAL CURVES GIVEN. THE BEHAVIOR OF CARS IS DETERMINED BY THE SLIP ANGLE OF THE FRONT AND REAR WHEELS AND THE RELATION BETWEEN THEM. BY EVALUATING THE SLIP ANGLE TO THE RATIO OF SIDE FORCE TO WEIGHT OR CORNERING RATIO, THE RESULTS OF TESTS BECOME APPLICABLE TO CURVES OF DIFFERING RADII AND TO CARS DRIVEN AT ALL SPEEDS. DIFFERENCE IN UNDERSTEERING AND OVERSTEERING CARS IS EXPLAINED. UNDERSTEERING CARS ARE FOUND TO HANDLE BETTER AND REQUIRE LESS WIDTH OF LANE ON CURVES. MAXIMUM CORNERING RATIO IS FOUND BY TESTS TO BE ABOUT 50 PER CENT. THIS INDICATES THAT NO HIGHWAY SHOULD BE CONSTRUCTED WITH A RADIUS OF CURVATURE WHICH WILL CAUSE A CAR TRAVELING AT MAXIMUM SPEED TO DEVELOP A CORNERING RATIO ABOVE THIS VALUE. /AUTHOR/

• Record URL:
  • https://onlinepubs.trb.org/Onlinepubs/hrbproceedings/17/17Pt1-012.pdf
• Supplemental Notes:
  • Vol 17, ParT I, PP 202-214, FIG, 1 PHOT. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved.
• Authors:
  • FOX, M L
  • Johnson, W C
  • Moyer, R A
• Publication Date: 1938

Media Info

• Media Type: Digital/other
• Monograph Title: Proceedings of the Seventeenth Annual Meeting of the Highway Research Board Held at Washington, D.C. November 30, December 1, 2, 3, 1937. Part I
• Serial:
  • Highway Research Board Proceedings
  • Volume: 17
  • Publisher: Highway Research Board

Subject/Index Terms

• TRT Terms: Centrifugal force; Curvature; Highway curves; Highway design; Speed; Steering; Test procedures; Vehicle characteristics; Wind pressure
• Uncontrolled Terms: Lateral loads; Relationships
• Old TRIS Terms: Cornering (Vehicle)
• Subject Areas: Design; Highways;

Filing Info

• Accession Number: 00203488
• Record Type: Publication
• Files: TRIS, TRB
• Created Date: Aug 15 1971 12:00AM