Access Control near Highway Interchanges

Abstract:

Objectives

  • Review origin of current guidelines for access separation from interchange ramps
  • Review recent Virginia study on the relationship between access spacing from interchange ramps and crash rates
  • Suggest new standards for the optimum access point spacing

 

Findings and Recommendations: Access Spacing from Interchange Ramp

  • Key findings include:
    • Regardless of geometric and traffic factors, the crash rate:
      • Is dramatically lower at 750 ft and 990 ft spacing from ramps
      • Is minimal at 1,320 ft
    • No safety improvement: 2,640 ft (1/2 mile) spacing vs. 1,320 ft (1/4 mile)
    • No significant difference between urban and rural ramps.
  • Safety justification for managing access near ramps – easy to understand, practical, politically acceptable.
    • Example:  VA Governor’s Transportation Strategic Plan goal:
      • “Improve safety across all modes of transportation by reducing transportation related injuries, fatalities, crashes.”
Slide List:
  1. Access Control at Highway Interchanges 
  2. Objectives
  3. AASHTO Policy on Design Standards Interstate System (2005)
  4. Origin of 100’/300’ Standard
  5. 100’ Urban, 300’ Rural Spacing:
  6. Crashes, Congestion
  7. 2003 TRB Access Management Manual
  8. NHRCP Report 420 Impacts of Access Management Techniques (1999)
  9. 1996 “Interchange Access Management” Background Paper #2 by R. Layton
  10. NCHRP Synthesis 332
  11. Access Management on Crossroads in the Vicinity of Interchanges (2004)
  12. Problem Statements
  13. Access Spacing from Interchange Ramps
  14. VDOT Sponsored Research Study
  15. Methodology
  16. Geometric Data Collection
  17. Windshield View Video Logs –
  18. Elements not visible from aerial photo
  19. Geometric Attributes of 186 Locations
  20. Traffic and Crash Data
  21. Plotting the Crash, Traffic, & Geometric Data 
  22. Qualitative Data Analysis
  23. Type of First Access
  24. Signalized and Unsignalized Average Crash Rates
  25. Crash Rate for Rural vs. Urban
  26. Crash Rate for Rural and Urban
  27. Medians Improve Safety
  28. Findings and Recommendations
  29. Access Spacing from Interchange Ramp
  30. Findings and Recommendations
  31. Access Spacing from Interchange Ramp
  32. Findings and Recommendations
  33. Access Spacing from Interchange Ramp
  34. For information 
  • Posted on: Fri, 08/30/2013 - 22:55
  • By: fbroen
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