Merge Sign Available Distance Proposal
Jeff D. Conrad
September 29, 2005

Proposal (8-10 minutes)

To test at a variety of locations, driver perception of installing a Merging Distance sign below the typical merge sign near Entrance / Exit ramps to highways.

Basis

  • Merging Physics
    • distance = velocity * time
    • velocity = acceleration * time
    • acceleration = force / mass
  • Variabilty
    • cars/trucks
    • drivers
    • physical merging distance
    • temporal conditions
      • Ramp Headway Factor - room to merge on highway
      • Minimum Ramp Time - time required on ramp due to interference, queing, and other vehicles
      • Weather (Visibility and control)
  • Statistics
    • Speed variance - a measure of the actual vehicle travel speeds above and below the average travel speed. Crash rates increase as the variance increases.
    • Fatalities near entrance/exit ramps
      Fatal Crashes 518 (529 in 1999)
      Vehicles 686
      Persons 1,118

  • Traffic Literature
    • "Impacts of heavy vehicles in the vehicle stream are more pronounced at shorter weaving distances" (Venglar et al)
  • Benefits
    • Reduction in all accident types
      • Stop-slowing
      • Ran off road
      • Sideswipe-cutoff (18%) - One vehicle is struck in the side by another vehicle that is changing lanes.

  • Test
    • One city or suburb
    • Variety of entrances
    • Minimize proximity effects

  • Potential issues
    • Beware of an on ramp lane forming an additional lane and then becoming an Exit Only lane, sometimes within a very short distance.

Test Sign

Survey

  • Sample 100 residents of city.
  • Did they drive upon highway entrances where the test signs were installed?
  • Did they notice the signs?
  • Did they consider the information helpful?
  • Did they have any experiences they would like to share?
  • Would they like to see the distances on other entrances?

Questions/Answers (3-5 minutes)

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References:

  • National Center for Statistics and Analysis. 2005. Fatality Analysis Reporting System (FARS) Retrieved September 29 from: http://www-fars.nhtsa.dot.gov
  • Campbell, B. N., Smith, J. D., and Najm W. G. 2004. Analysis of Fatal Crashes Due to Signal and Stop Sign Violations Retrieved September 29, 2005 from: http://www-nrd.nhtsa.dot.gov/departments/nrd-12/809-779/images/FARS%20Violation%20DOT%20HS%20809%20779.pdf
  • Zhang, M., Kim, T., Nie, X., and Jin W. 2001. Evaluation of On-ramp Control Algorithms. Retrieved September 29, 2005 from: http://www.nawgits.com/icdn/Final_report.pdf
  • Venglar, S., Fenno, D., Goel, S., and Schrader, P. 2005. Project Bulletin 4160-4B. Project 0-4160: Operating Freeways with Managed Lanes.