Overview

1. 90th Annual T.H.E.ConferenceSign RetroreflectivityMike StaggsMobility & Safety Team LeaderFederal Highway Admin. - Ilinois

2. Overview • Retroreflectivity – What is it? • Materials - How do retroreflective materials work? • Impact - Why is it important? • Visibility issues - How do the pieces fit together? • Status of future requirements • What should be done now?

3. What is Retroreflectivity? • “Reflective” is a generic term and is the reason we can see objects • Every surface is reflective!

4. Types of Reflectivity

5. What Is a Retroreflector? • Material that directs light back to the source • Bead retroreflectivity • Light reflects off reflector coat behind a small bead • Cube corner material • Light reflects off three sides of prism

6. Sheeting Cross Section

7. Why is Geometry Important? • Light from source reflected back in a cone shape • Retroreflectivity decreases as angles increase • Intensity of reflected light decreases with distance from cone axis More dim Dimmer Bright

8. Why Do We Install Signs? Why? Engineering Decision? To help drivers YES! Guidance is MUTCD? Yes

9. Nighttime - few cues remain Task more difficult Daytime - many cues available Driver task relatively easy Why is it Retroreflectivity Important? • Critical for nighttime driving

10. Crash Data: Non-Daylight

11. Can we judge retroreflectivity during the day?

12. Problem: Retroreflectivity Degrades Over Time

13. Visibility Issues What do drivers see? What do headlights do? What is the vehicle impact?

14. Driver Luminance Needs • Starting at age 20, the amount of light needed to see an object the same way doubles every 13 years

15. Minimum Retroreflectivity What is the concept? Why is it important? What has happened? What are the recommendations? When will it happen?

16. What is the Concept? • Current specifications establish minimums for new materials • Devices must be visible to be effective • In-service minimum values will establish the end-of-service life for devices • Devices not meeting in-service minimums should be replaced

17. Current MUTCD Language • 2A.06: … basic requirements … uniformity in design includes retroreflectivity… high visibility by day and night • 2A.08: … shall be retroreflective … show same shape and color day and night • 2A.22: should have adequate retroreflectivity … should establish schedule for inspecting (both day and night)

18. Congressional Legislation 1993 DOT Appropriations Act – “The Secretary of Transportation shall revise the MUTCD to include a standard for a minimum level of retroreflectivity that must be maintained for traffic signs and pavement markings which apply to all roads open to public travel.”

19. AASHTO Task Force • Created in November 1998 • Represents states, cities, counties, academia, private industry, and FHWA • Recommendations received for signs in December 2000

20. AASHTO Resolution • Desirable to assure adequate night visibility for signs • Regular assessments of retroreflectivity or planned replacements of signs “is necessary”

21. AASHTO Recommendations • Minimum requirements should be simple • Do not publish numerical values in MUTCD • Publish separately and reference in MUTCD • Need alternatives other than measured retroreflectivity to assure adequate nighttime visibility • Agencies should choose from optional methods • Provide 6 years to implement

22. AASHTO’s 4 Proposed Methods of Addressing Retroreflectivity • Minimum sign retroreflectivity values • Minimum nighttime sign legibility distances • Nighttime visual sign inspection by calibration or sample • Maximum service life of signs

23. Research Recommended Minimum Values

24. Sign Materials • Engineering grade • ASTM Type I • Super engineering grade • ASTM Type II • High intensity • ASTM Type III • Microprismatic • ASTM Types IV, VII, VIII, IX • Roll-up • ASTM Type VI

25. Impact on Your Agency? • What is our sign maintenance system now? • Do we have a system that addresses nighttime visibility of signs? • What is the nighttime visibility condition of our signs? • What types of sheeting do we use now?

26. 5 Methods to Assess & Manage Retroreflectivity • Visual Nighttime Inspection – the retroreflectivity of an existing sign is assessed by a trained sign inspector conducting a visual inspection from a moving vehicle during nighttime conditions

27. 5 Methods to Assess & Manage Retroreflectivity • Visual Nighttime Inspection – the retroreflectivity of an existing sign is assessed by a trained sign inspector conducting a visual inspection from a moving vehicle during nighttime conditions

28. 5 Methods to Assess & Manage Retroreflectivity • Measured Sign Retroreflectivity – sign retroreflectivity is measured using a retroreflectometer. Signs with retroreflectivity below the minimum levels need replacement.

29. 5 Methods to Assess & Manage Retroreflectivity • Expected Sign Life – When signs are installed, the installation date is labeled or recorded so that the age of a sign is known. Expected life based on warranties, test deck measurements, or actual measurements.

30. 5 Methods to Assess & Manage Retroreflectivity • Blanket Replacement – All signs in an area/corridor, or of a given type, are replaced at specified intervals. This eliminates the need to assess retroreflectivity or to track life of individual signs.

31. 5 Methods to Assess & Manage Retroreflectivity • Control Signs – replacement of signs in the field is based on the performance of a sample of control signs. The control signs may be a small sample located in a maintenance yard or a sample of signs in the field. The control signs are monitored to determine the end of retroreflective life for the associated signs.

32. Sign Retroreflectometers ~$6,000 ~$8,000 920 920 SE Retrosign ~$9,000 Impluse RM SMARTS Van ~$240,000

33. Questions?http://safety.fhwa.dot.gov