VISIBILITY PROBLEMS IN CREST VERTICAL CURVES
THE LENGTH OF CREST VERTICAL CURVE IS GOVERNED BY VISIBILITY CONSIDERATIONS. THE MINIMUM LENGTH IS BASED ON THE STOPPING SIGHT DISTANCE; THE MAXIMUM LENGTH IS BASED ON THE PASSING SIGHT DISTANCE, AND OVERTAKING IS ALLOWED THROUGHOUT ITS LENGTH. THE OBJECT OF THE PRESENT PAPER IS THEORETICAL DETERMINATION OF THE ZONE OF OVERTAKING VISIBILITY IN A CURVE DESIGNED ON A BELOW-MAXIMUM BASIS. THE ANALYSIS COVERS 2 CASES: (1) OVERTAKING VEHICLE INSIDE AND ONCOMING VEHICLE OUTSIDE THE CURVE AND (2) BOTH VEHICLES OUTSIDE THE CURVE. THE CORRESPONDING CURVE GEOMETRIES WERE ALSO CONSIDERED. THE EQUATIONS OBTAINED WERE COMPUTER-SOLVED FOR CURVES WITH SLOPE DIFFERENCE RANGING FROM 2 TO 12 PERCENT, PASSING SIGHT DISTANCES CORRESPONDING TO THE DESIGN SPEED RANGE OF 50 TO 110 KM/HR, AND LENGTH LIMITS CORRESPONDING TO THE STOPPING AND PASSING SIGHT DISTANCES RESPECTIVELY. RESULTS WERE RENDERED IN CONVENIENT GRAPH FORM, PERMITTING DETERMINATION OF THE TYPE OF DIVISION LINE AND THE LENGTH OF THE NO-OVERTAKING ZONE TO BE MARKED ON A 2-WAY 2-LANE HIGHWAY IN THE VICINITY OF THE CURVE. THE LENGTH OF THE NO-OVERTAKING ZONE INCREASES WITH THE OVERALL LENGTH OF THE CURVE, UP TO THE MAXIMUM (UNRESTRICTED OVERTAKING). THE CONCLUSION IS THAT, IN ORDER TO REDUCE THE NO-OVERTAKING ZONE IN BELOW-MAXIMUM CASES, IT SHOULD PREFERABLY BE AS SHORT AS POSSIBLE WITHIN THE REQUIREMENT LIMITS OF OVERTAKING VISIBILITY AND DRIVING CONVENIENCE. /AUTHOR/
- Record URL:
-
Supplemental Notes:
- Paper sponsored by Committee on Operational Effects of Geometrics. 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:
- Livneh, M
- Prashker, J
- Uzan, J
- Publication Date: 1970
Media Info
- Media Type: Print
- Features: Figures; References; Tables;
- Pagination: pp 76-84
- Monograph Title: Relationships of highway geometry to traffic accidents
-
Serial:
- Highway Research Record
- Issue Number: 312
- Publisher: Highway Research Board
Subject/Index Terms
- TRT Terms: Curves (Geometry); Design speed; Length; Passing; Passing sight distance; Stopping sight distance; Theory; Visibility
- Uncontrolled Terms: Vertical curvature
- Old TRIS Terms: Crest
- Subject Areas: Highways; Safety and Human Factors;
Filing Info
- Accession Number: 00221083
- Record Type: Publication
- Files: TRIS, TRB
- Created Date: Oct 26 1970 12:00AM