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WYDOT’s Variable Speed Limit Project

WYDOT’s Variable Speed Limit Project. Presented to the Oregon DOT December 2, 2010. Outline. Explain background behind VSL project Detail location of the project Variable Speed Limit Sign Technology VSL Engineering Approach Protocol Explain results Explain future for VSL project(s).

joshua-fischer
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WYDOT’s Variable Speed Limit Project

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  1. WYDOT’s Variable Speed Limit Project Presented to the Oregon DOT December 2, 2010

  2. Outline Explain background behind VSL project Detail location of the project Variable Speed Limit Sign Technology VSL Engineering Approach Protocol Explain results Explain future for VSL project(s)

  3. Background Information

  4. I-80 Background Information Major east-west commerce route 2035 Projections Source: FHWA Freight Management and Operations Division

  5. I-80 Background Information >50% of I-80 traffic is heavy trucks AADT 11,000 vehicles per day Frequent adverse weather conditions Strong winds Heavy snow Blowing snow Visibility problems Drifting of snow Icy conditions

  6. I-80 - Background Information Frequent closures Inconvenience to some travelers Economic impact Crash rate is higher than average in the VSL corridor Several multi-vehicle fatalities in the corridor

  7. Blizzards in Wyoming

  8. March 26, 2006 Photo courtesy of Tim McGary

  9. March 26, 2006 Photo courtesy of Tim McGary

  10. March 26, 2006 Photo courtesy of Tim McGary

  11. March 26, 2006 Photo courtesy of Tim McGary

  12. March 26, 2006 Photo courtesy of Tim McGary

  13. March 26, 2006 Photo courtesy of Tim McGary

  14. December 23, 2007 Icy roads with ground blizzards 3 members of a Colorado family killed 17 year old daughter was lone surviving family member

  15. Legislation (WS-31-5-302) Legislation went into effect 7/1/2008 Grants authority to set the speed limit based on “vehicle or weather emergency” “…differing limits may be established for different times of day, different types of vehicles, varying weather conditions, and other factors bearing on safe speeds, which shall be effective when posted upon appropriate fixed or variable signs.�” http://legisweb.state.wy.us/statutes/statutes.aspx?file=titles/Title31/T31CH5AR3.htm

  16. Definitions • Seasonal speed limit – Speed reduction to 65 mph from October 15 to April 15 • Variable speed limit – Speed reduction based on weather conditions or other factors that affect the safety of travelers.

  17. Project Location • I-80 in southeast Wyoming, between Rawlins and Laramie

  18. Intelligent Transportation SolutionVariable Speed Limit

  19. Project Location • Peterson Int. (MP 238.15) to Quealy Dome (MP 290.44) 17.45 miles 34.84 miles

  20. Sensor Technologies Road Weather Information System

  21. Sensor and Sign Locations • Road Weather Information Sensors ( )

  22. Sensor Technologies Speed Sensor

  23. Sensor and Sign Locations • Speed Sensors ( )

  24. Sign Technologies

  25. Complete System • VSL ( )

  26. VSL Approach Provide timely and site-specific regulatory speed limit to guide travelers through the corridor Conduct research to determine if a positive benefit is realized and to develop processes - research conducted by Dr. Rhonda Young

  27. VSL Approach VSL’s located at interchanges to inform people as soon as they enter the system VSL located on both median and shoulder side for visibility

  28. VSL Approach • Focus: tighten speed distribution

  29. Representative Scenario

  30. VSL Approach • Encourage drivers to travel at the same speed AND set a speed that is appropriate to conditions • System would act more like a train • Risk of crashes is reduced • Risk of severe crash is reduced • Risk of closure is reduced • Social and Economic benefits

  31. VSL Process

  32. Protocol • Cooperation between: • Troopers • Maintenance • TMC • Process takes about a minute to: • Receive request for speed reduction • Reduce speed at roadside • Inform the public (website, phone system, text/email notification)

  33. VSL Process • Interim Protocol/Policy • WHP or Maintenance may lower speed based on visual inspection • TMC can lower speed if speed varies more than 15 mph and no one is available for visual inspection • Requires visual inspection to raise speed limit • Interim Protocol Used until Control System completed

  34. Interstate 80 – VSL Project

  35. Interstate 80 – VSL Project

  36. Research Results(University of Wyoming)

  37. Effectiveness of VSL in Lowering Speeds • During the initial period of VSL implementation (Feb-April 2009) statistical models showed that the VSL reduced speed postings lowered the average speeds by 5 to 7.5 mph for every 10 mph in posted speed reduction • This was in addition to speed reductions that could be accounted for by the weather conditions

  38. Effectiveness of VSL in Lowering Speeds • During the period from October 15-December 15, 2009 further statistical modeling showed that the VSL reduced speed postings lowered the observed speeds from 6 to 8 mph for every 10 mph in posted speed reductions • This was in addition to speed reductions that could be accounted for by the weather conditions • Indicates that the speed reductions were not just due to drivers reacting to the newly installed system during the first season

  39. Research Results • Following slide demonstrates actual storm - December 1 and 2, 2009 • Storm broken into four stages for analysis purposes

  40. Dry and Clear Storm Begins to Impact Roadway VSL In Effect Storm Clears (VSL In Effect)

  41. Research Results • The seasonal speed limit of 65 mph is not effective on clear and dry days • Average speed during seasonal speed limit period is within 1.5 mph of summer speeds • Lack of compliance may indicate driver disrespect of speed limit signs

  42. Crash Data The nature of crash data requires 3-5 years of observation before final conclusions can be made about the affect of a roadway change. With that said… The number of crashes over the last year (April 2009-April 2010) are lower than any of the previous eight years

  43. Crash Data First Full Year of VSL

  44. Future of VSL project • Further research with UW • Attempting to develop a control system • First option will be take on-scene report (Patrol or Maintenance) • In the absence of visual inspection, use control system • Base control system on speeds and weather conditions

  45. Control System Use weather variables that most affect speed variances (based on research) Visibility Surface condition Etc. Develop processes to adjust speed limit when speed variation and/or known weather problems exist

  46. Results Need to address Interim Protocol

  47. Future Plans

  48. Future Plans • Continue Research – Determine contributing variables that indicate a reduction or increase in speed is warranted • Don’t always have eyes on the road • Variables • Wind • Surface conditions • Visibility

  49. Future VSL’s

  50. Questions/Comments

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