OPERATIONAL EFFECTS OF SOME ENTRANCE RAMP GEOMETRICS ON FREEWAY MERGING

TIME-LAPSE, AERIAL PHOTOGRAPHS WERE TAKEN AT 29 ENTRANCE RAMPS IN SEVEN CITIES ACROSS THE COUNTRY AND DATA FROM 23 OF THESE ENTRANCE RAMPS ARE PRESENTED. THE RAMPS HAD A WIDE RANGE OF GEOMETRICS, I.E., ACCELERATION LANE LENGTHS 240 FT TO 1,500 FT AND CONVERGENCE ANGLES BETWEEN 1 AND 14 DEG. THE GEOMETRIC ELEMENTS FOR WHICH THE OPERATIONAL EFFECTS WERE MOST CAREFULLY EVALUATED ARE ACCELERATION LANE LENGTH, ANGLE OF CONVERGENCE AND RAMP GRADE. OPERATIONAL CHARACTERISTICS EXAMINED WERE SPEED OF RAMP VEHICLES AT THE RAMP NOSE AND AT THE MERGE POINT, CHANGE OF SPEED OF RAMP VEHICLES BETWEEN THE RAMP NOSE AND THE MERGE POINT, THE RELATIVE SPEEDS OF VEHICLES AT THE RAMP NOSE AND AT THE MERGE POINT, THE ACCEPTED GAP NUMBER AND THE DISTRIBUTION OF POINTS OF ENTRY ONTO THE FREEWAY. ALL OF THESE ANALYSES WERE MADE DURING PERIODS IN WHICH THE FREEWAY OPERATING SPEED WAS IN EXCESS OF 40 MPH. EACH OF THE VARIABLES, ACCELERATION LANE LENGTH, ANGLE OF CONVERGENCE AND RAMP GRADE, WERE FOUND TO HAVE A GREAT EFFECT ON THE MERGING OPERATION. GENERAL CONCLUSIONS REGARDING ENTRANCE RAMP DESIGN ARE PRESENTED. /AUTHOR/

• Record URL:
  • http://onlinepubs.trb.org/Onlinepubs/hrr/1967/208/208-003.pdf
• Supplemental Notes:
  • Paper sponsored by Committee on Operational Effects of Geometrics and presented at the 46th Annual Meeting. 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:
  • Wattleworth, Joseph A
  • Buhr, Johann H
  • DREW, DONALD R
  • Gerig Jr, Frank A
• Discussers:
  • Worrall, R D
  • Blackburn, James D
  • May Jr, Adolf D
  • Wattleworth, Joseph A
  • Buhr, Johann H
  • DREW, DONALD R
  • Gerig Jr, Frank A
• Publication Date: 1967

Media Info

• Media Type: Digital/other
• Features: Figures; References; Tables;
• Pagination: pp 79-122
• Monograph Title: Freeway traffic characteristics
• Serial:
  • Highway Research Record
  • Issue Number: 208
  • Publisher: Highway Research Board

Subject/Index Terms

• TRT Terms: Acceleration lanes; Aerial photography; Angularity; Freeways; Geometric design; Length; Merging traffic; Ramps; Slopes
• Uncontrolled Terms: Angles; Convergence; Grade (Slope)
• Subject Areas: Design; Highways; Operations and Traffic Management;

Filing Info

• Accession Number: 00225111
• Record Type: Publication
• Files: TRIS, TRB
• Created Date: Feb 20 1994 12:00AM