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Wyoming DOT

Wyoming DOT. Place guardrail when there is a fill slope of 3:1 or steeper located within the clear zone Their clear zone requirements match the AASHTO guide. Alaska DOT. Developed a spreadsheet for conducting a cost-effectiveness analysis on variant obstacles

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Wyoming DOT

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  1. Wyoming DOT • Place guardrail when there is a fill slope of 3:1 or steeper located within the clear zone • Their clear zone requirements match the AASHTO guide

  2. Alaska DOT • Developed a spreadsheet for conducting a cost-effectiveness analysis on variant obstacles • Supplements the AASHTO Roadside Design Guide • Returns an accident prediction output and a project cost output • Used to provide relative estimates for comparison of alternatives, not to determine an exact cost for accidents

  3. Survey of State DOTS

  4. Summary • 50 states contacted via email or web submission forms • 17 responses as of February 9 • Expecting responses from a few additional states (Alaska and Ohio)

  5. Who deals with Guardrail Maintenance Division referred to most often Personnel/Divisions with expertise on funding allocation for guardrails • Others: • Roadway Design • Policy and Budget • Design engineer • Traffic engineer • Highway Safety engineer • State Traffic engineer • Highway Operations

  6. Recommendations from DOTs • Variety of responses: • Benefit-cost ratio or other cost-effectiveness analysis • Guardrail projects done in conjunction with other scheduled projects • Compare guardrail accident rates to total accident rates and prioritize based on guardrail accident rates • Look at high accident areas first, high ADT areas second • Follow AASHTO 350 implementation Task Force summary • Some states noted that they too are in need of assistance in this area

  7. Databases Utilized • 6 respondents have some sort of guardrail inventory • Information included: • Amount of guardrail installed • Guardrail type, end treatment, location, length • Information on completed guardrail projects

  8. Methodologies Employed NCHRP 350 B/C evaluation sometimes used

  9. Standards • Roadside Design Guide • NCHRP 350 • Some states develop own policies • Judgment and expertise

  10. Factors for Upgrade • Physical Characteristics: • Obsolescence • Height • Lack of blockouts • Substandard end treatment • Insufficient length of need • Rail condition • Crashworthiness • Other Factors: • Upgrade with scheduled projects • Accident history • Presence of a 3R/4R project • Compliance with 350 • New standards • FHWA mandates

  11. Survey Work to be Done • Continue compiling responses • Perform necessary follow-up on responses • Incorporate survey responses within working paper on previous work

  12. Evolving Guardrail Standards and Resource Allocation

  13. Motivation - How Standards Affect Resource Allocation • Old versus new • Run of rail versus end treatment • No installation versus new • Repair versus replacement • Costs • Upgrade: Removal and replacement • New: Installation costs • Disposal and Recycling • Lifecycle Costs

  14. Objectives • Gain understanding for characteristics of multiple guardrail systems • Grasp weaknesses in current response to evolving standards • Put strengths together for a state-of-the-art model for resource allocation

  15. Mathematical Models and Resource Allocation • Review and evaluate models to aid in decision-making processes • Develop state-of-the-art decision tool

  16. Mathematical Models and Resource Allocation • Devise Review (Mesterton-Gibbons, 1995);(Nicholson, 1989); (Hillier-Lieberman, 1995) • FHWA • Videos (Trinitron and Syro) • AASHTO

  17. International Comparison of Guardrail Standards Switzerland Japan France

  18. Switzerland • No barriers should be shorter than 50 meters • Barriers where ADT >= 10,000 or where average speeds are > 75 km/h

  19. Switzerland • On any roads where: • Retaining walls and bridges, if height exceeds 2 meters • Parallel with railways, or watercourses deeper than 1 meter • Large obstacles must beprotected 50 – 60 meters before the obstacle

  20. Switzerland • Trees closer than 10 meters to the road are removed whenever possible • On national divided highways the federal administration requires the installation of median barriers without regard to traffic volume

  21. Switzerland • On divided highways • Along the median • Along fills with heights exceeding 4 meters and slopes steeper than 1.5:1

  22. Switzerland • On roads with less than 10000 vehicles ADT barriers should only be installed in cases where the conditions are aggravated by complications such as, • Along curves, if the radius of a curve is smaller than the prescribed minimum for the design speed • If the roadway is often covered with sleet

  23. Japan • A study by the Japanese Public Works Research Institute seeks to evaluate the effect on accidents of crash barriers from a strictly economic standpoint, using the formula: • B = (Nb * Db) – (Na* Da) – M – I

  24. Japan Where • B = benefit from guardrail construction • Nb = number of run-off accidents expected before guardrail installation • Db = expected damage in a run-off accident before guardrail installation • Na = number of collision accidents expected after guardrail installation

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