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Background and History

Background and History. MUTCD Sign Retroreflectivity. Purpose of Module. Background Describe sign retroreflectivity concepts Understand nighttime visibility issues MUTCD Summarize new requirements Describe retroreflectivity methods and procedures. Retroreflection. What is it?.

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Background and History

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  1. Background and History MUTCD Sign Retroreflectivity

  2. Purpose of Module • Background • Describe sign retroreflectivity concepts • Understand nighttime visibility issues • MUTCD • Summarize new requirements • Describe retroreflectivity methods and procedures

  3. Retroreflection What is it? • A ratio of the amount of light returned from a sign versus the amount hitting the sign • A way to measure the efficiency of a material Light OUT of sign Light INTO sign = Retroreflectivity

  4. Is Retroreflectivity Important? • Importance has increased • Not a part of any educational curriculum • Your agency now responsible Of Course Retroreflectivity is important!

  5. Why Do We Install Signs? Required by MUTCD? NO Engineering Decision? YES! Why? To help drivers (including older)

  6. Retroreflective Signs Daytime signing here is ________ Nighttime signing here is _________

  7. Night Travel and Crashes Source: National Safety Council

  8. Fatal Crash Data: Non-Daylight

  9. Night Safety Problem • Glare from opposing traffic • Adverse weather conditions • Aging driving population • Visible traffic signs • Driver expectancy • Fatigue • Increased alcohol use

  10. Driver Luminance Needs Starting at age 20, the amount of light needed to see doubles every 13 years

  11. Younger drivers:

  12. Young drivers Greater levels of relative nighttime exposure Sullivan & Flannagan (UMTRI-2009-4) Younger drivers drive proportionally more of their miles at night (NPTS, 2001). Source: UMTRI, Night Vision Enhancement Systems Presentation

  13. Young drivers Especially high nighttime fatal crash risk Sullivan & Flannagan (UMTRI-2009-4) Massie, Campbell, Williams (1995). Source: UMTRI, Night Vision Enhancement Systems Presentation

  14. Daytime Many cues available Driver task relatively easy Nighttime Few cues remain Task more difficult Visual Cues Retroreflectivity provides nighttime guidance

  15. Degraded Stop Sign ..

  16. Typical Outdoor Durability Testing Type III 45 degree south facing Retroreflectivity Type II Type I 0 10 20 30 40 50 60 70 80 Age (months)

  17. 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.”

  18. Why Create Minimums? Daytime Nighttime

  19. Retroreflectivity Concepts

  20. RETROreflection

  21. RetroreflectionInformal Definition • A ratio of the amount of light returned from a sign versus the amount hitting the sign • A way to measure the efficiency of a material Light OUT of sign Light INTO sign = Retroreflectivity

  22. Retroreflectivity Cone Retroreflector Reflected light is brighter near light axis Reflected light gets dimmer as distance from light axis increases Light Source Direction

  23. Retroreflective Elements • Glass spheres and microsized prisms are the current technologies used to make sign materials retroreflective • The light is returned to the source in a cone shaped pattern

  24. Sign Sheeting Materials Engineering Grade Hi-Intensity Beaded Microprismatic

  25. Sign Sheeting

  26. Sheeting Types

  27. Summary • Does retroreflectivity by itself describe how bright a sign will look? • Everything else equal, how will a driver in a sports car see a nighttime sign versus a driver in a big truck?

  28. Key Nighttime Visibility Issues • Sign • Location • Sheeting materials • Headlamps • Amount of light for signs • Driver • Visual capabilities • Comfort level • Vehicle • Size

  29. Sign Conditions

  30. Rural vs Urban Areas • The minimum retroreflectivity levels in the MUTCD are based on • Older drivers vision • Sign recognition and legibility • Rural areas without background complexity • What happens in urban areas?

  31. Can you see the sign?

  32. Key Issue: Headlamps • Out of control of traffic engineers • Evolving considerably in last decades

  33. Headlamps • Sealed Beam Pattern • Modern Cutoff Pattern

  34. Key Issue: Drivers

  35. Cone Size is Important Cone of Retroreflection

  36. MUTCD Requirements MUTCD Sign Retroreflectivity August 2013

  37. Purpose of Module • Background • Describe sign retroreflectivity concepts • Understand nighttime visibility issues • MUTCD • Summarize new requirements • Describe retroreflectivity methods and procedures

  38. 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.”

  39. Concept of Minimum Levels • Premise – There is a minimum measure of night visibility for TCDs to meet driver needs. • Measure – retroreflectivity • Evolution: • 1993 Research • 1995 Adjustments (analytic, driver based) • 1998 Report • 2002 Updates & Consolidation

  40. New MUTCD Standard “Standard: Public agencies or officials having jurisdiction shall use an assessment or management method that is designed to maintain sign retroreflectivity at or above the minimum levels in Table 2A-3”

  41. Signs Provide Critical Information to Drivers But, Retroreflectivity Degrades Over Time When Do We Replace Signs? Retroreflectivity

  42. Can we decide to replace signs based on daytime inspections?

  43. What’s New? MUTCD Introduction (Compliance Dates): MUTCD Requirements June 13, 2014 regulatory and warning sign retroreflectivity at or above the established minimum levels

  44. MUTCD Requirements Table 2A-3 Minimum Maintained Retroreflectivity Levels¹ MUTCD Section 2A.08 Standard: Public agencies or officials having jurisdiction shall use an assessment or management method that is designed to maintain sign retroreflectivity at or above the minimum levels in Table 2A-3.

  45. Sign Retro Requirements MUTCD Section 2A.08 Guidance: Except for those signs specifically identified in Paragraph 6, one or more of the following assessment or management methods should be used to maintain sign retroreflectivity.

  46. Sign Retro Requirements Methods and Procedures Visual Nighttime Inspection Comparison Panel Procedure Calibration Signs Procedure Consistent Parameters Procedure Measured Sign Retroreflectivity Expected Sign Life Blanket Replacement Control Signs

  47. Sign Retro Requirements Methods and Procedures Visual Nighttime Inspection Uses trained personnel to observe traffic signs during the nighttime Key to this method is using an approved procedure to tie the inspection to the minimum values in Table 2A-3 Methods: Comparison Panel Procedure Calibration Signs Procedure Consistent Parameters Procedure

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