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Advancing Guardrail Standards and Cost-Effectiveness Analysis for Road Safety

This report focuses on the latest guardrail standard recommendations by the Wyoming DOT, aligning with AASHTO guidelines and using cost-effectiveness analysis to improve resource allocation. A survey of 50 state DOTs reveals insights into personnel with guardrail expertise and presents methodologies for evaluating guardrail performance, including NCHRP standards. This document aims to understand the dynamics between evolving standards, resource allocation, and accident prevention, advocating a more strategic approach to guardrail maintenance and installation across states.

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Advancing Guardrail Standards and Cost-Effectiveness Analysis for Road Safety

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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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