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FHWA Home / Safety / Roadway Departure / Workshops on Nighttime Visibility of Traffic Signs

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Cathy Satterfield
cathy.satterfield@dot.gov

Nighttime Visibility of Traffic Signs: Appendix I - Questions to be Considered

The FHWA should consider the following questions prior to publishing a proposed rule on minimum levels of in-service sign retroreflectivity. The questions are shown at the Arabic number level in the following outline. The small letters following most questions indicate potential answers to the question. The information in the report provides information on the public agencies' perspectives and opinions on many of these issues.

  1. General philosophy
    1. Overall goal
      1. What is the overall goal?
        1. To provide signs with a minimum level of retroreflectivity.
        2. To improve nighttime sign visibility.
        3. To improve nighttime safety.
        4. Other or a combination of the above.
      2. What is the relationship between retroreflectivity and visibility?
        1. Retroreflectivity is a sign property that is one of several factors that determines sign visibility. Examples of other factors that affect sign visibility include the amount of illumination reaching the sign; the positional relationship between the headlamps, sign, and driver; the luminance needs of the driver; and the transmissivity of the windshield.
        2. A sign can have sufficient retroreflectivity, but still not be visible for any number of reasons, i.e., sight distance obstructions, inadequate illumination, or dew on the sign.
        3. If the goal of the rulemaking is to improve nighttime sign visibility, then establishing minimum levels of in-service sign retroreflectivity is only one element of the overall effor
    2. MUTCD language
      1. What should the MUTCD address?
        1. Sign retroreflectivity.
        2. Sign visibility.
      2. How should the MUTCD language be formatted?
        1. "Shall" condition requiring action.
        2. "Should" condition recommending action.
      3. Should the MUTCD require/recommend a process or specific methods?
        1. The MUTCD can establish a general goal (such as providing reasonable nighttime sign visibility) and allow agencies to establish policies and procedures to meet the goal.
        2. The MUTCD can provide general options that an agency can use to meet the goal (such as visual nighttime sign inspections or measured sign retroreflectivity).
        3. The MUTCD can provide specific threshold criteria (such as a specific expected sign life for a given sheeting or a specific coefficient retroreflectivity [RA] value for a sign in a given situation).
    3. Congressional mandate
      1. What is required to establish the standard required by the mandate?
        1. Standard ("shall") language in the MUTCD.
        2. Guidance ("should") language in the MUTCD.
      2. What defines a minimum level of retroreflectivity?
        1. Numerical criteria presented in the MUTCD.
        2. A reference to numerical criteria in a supporting document.
        3. A recommendation to use a minimal level of retroreflective sheeting.
    4. Level of Detail
      1. How much information should be included in the MUTCD?
        1. All information that a jurisdiction will need to know, including values and procedures.
        2. General information that lets jurisdictions make their own decisions.
        3. References to supplemental documents that agencies can use.
      2. How will professionals know about research and other guidelines if it is not referenced in the MUTCD?
      3. What signs should be included/excluded from the process?
  2. Factors related to alternative methods
    1. Measured sign retroreflectivity
      1. What is the precision level associated with field measurement of sign retroreflectivity?
      2. Are the minimum values based on reasonable assumptions?
      3. What is the appropriate balance between scientific accuracy (more values) and practical implementation (fewer values)?
      4. How should non-representative situations be addressed in the minimum values, if at all?
        1. Signs in urban areas.
        2. Signs in high demand locations.
        3. Signs in disadvantaged locations.
      5. Which signs should be measured?
        1. All signs.
        2. Control signs.
        3. Questionable signs based on visual inspection.
        4. Signs over a specified age.
      6. Should a sign management system be an essential or required element in tracking sign retroreflectivity values?
    2. Nighttime visual inspection
      1. What is the accuracy of a nighttime sign inspection process?
      2. How often should nighttime sign inspections be conducted?
      3. Should nighttime inspections be recommended ("should" condition)?
      4. Who should conduct the nighttime sign inspections?
        1. Sign field personnel.
        2. Other field personnel.
        3. Engineering personnel.
        4. Non-technical personnel.
        5. Personnel that do not have budget or maintenance responsibility for the signs being inspected.
        6. Police and other agency personnel.
      5. Should sign inspectors receive formal training?
      6. Should there be a certification program for sign inspection?
      7. What vehicle should be used to conduct inspections?
      8. Should there be a formal procedure for aiming the inspection vehicle's headlamps prior to conducting the inspection?
      9. Should the subjective evaluation be tied to the objective minimum retroreflectivity levels through some procedure?
        1. Calibration signs.
        2. Formalized training.
    3. Expected sign life
      1. What should be the expected life of different sign materials?
        1. Seven years for Types I and II.
        2. Ten years for Types III, VII, VIII, and IX.
      2. How long will microprismatic materials last?
      3. Should there be a standard method of indicating sign age?
        1. Sticker on front or back of sign.
      4. Should there be a national program to develop expected sign life information on various sign materials?
    4. Inspection panels
      1. How many inspection panels are feasible to use?
      2. Will inspection panels be required for each sign material and each color?
      3. How will the inspection panels be manufactured so that they have retroreflectivity levels at or near the minimum levels?
    5. Control signs
      1. How representative are control signs?
      2. How many control signs are needed to accurately represent the signs in the field?
    6. Combination of methods and new methods
      1. Should FHWA define the acceptable methods?
      2. Should there be recommendations on how the methods can be combined?
  3. Factors related to supplemental information
    1. Document
      1. Who should publish the supplemental document?
      2. What should be the relationship between the document and the MUTCD?
      3. Should the document be included as part of the proposed rule or made available outside of the proposed rule?
    2. Content
      1. What should be included in the document?
        1. Minimum retroreflectivity values.
        2. Procedures for measuring retroreflectivity.
        3. Procedures for conducting nighttime inspections.
        4. Recommendations for sheeting service life.
        5. Methods of monitoring sheeting service life.
        6. Procedures for using inspection panels.
        7. Recommendations on how to manufacturer inspection panels.
  4. Factors related to rulemaking
    1. Publicity
      1. How should the profession be informed of the proposed rule?
      2. What should the FHWA do to present status information to the profession?
      3. What should be covered in the proposed rule?
        1. MUTCD language.
        2. Supplemental document (or should it be available, but not part of the proposed rule)
        3. Implementation time frame - compliance period.
        4. Expected impacts and benefits to jurisdictions based on general analysis.
  5. Factors related to implementation
    1. MUTCD
      1. Should the MUTCD present alternative methods other than minimum retroreflectivity?
      2. How much information should the MUTCD contain about alternative methods?
      3. Should the MUTCD reference a supplemental document?
      4. Should retroreflectivity values be presented in the MUTCD or a supplemental document?
      5. What should be addressed in the supplemental document?
      6. Will the MUTCD language address anything that is not already covered in other sections of the MUTCD?
    2. Tort liability
      1. What are the expected tort impacts of MUTCD language?
      2. Will MUTCD language create tort exposure that does not already exist?
      3. How can the MUTCD language be structured to minimize tort exposure for jurisdictions that are providing reasonable nighttime sign visibility?
      4. What are the tort implications of information contained in a separate document?
    3. Resources
      1. What are the fiscal impacts of the various implementation methods?
      2. What are the personnel impacts of the various implementation methods?
      3. What training will be needed for jurisdiction personnel?
      4. To what extent can police and other agency personnel be utilized as part of their normal duties to identify signs needing replacement?
      5. What will be the record keeping requirements of implementation?
      6. To what extent will agencies have to purchase instruments?
    4. Benefits
      1. What are the expected benefits to road users?
      2. What are the expected benefits to jurisdictions?
    5. Quality
      1. Will the values improve or reduce the quality (relative to nighttime visibility) of signs maintained by jurisdictions?
      2. What signs, if any, should be exempted from visibility and/or retroreflectivity criteria?
    6. Replacement
      1. What proportions of a jurisdiction's signs should be replaced each year?
      2. Will the replacement options be consistent with the expected replacement rate?
      3. What is the time frame for replacement of signs to meet the MUTCD language?
      4. Should implementation be staggered over time or just a final date?
        1. National Highway System, rural roads, urban roads.
        2. Regulatory, warning, guide.
        3. 55+ mph, 35-50 mph, 0-30 mph.
      5. Is it appropriate to continue using low performing sheeting (i.e., Type I [Engineering Grade] or Type II [Super Engineer Grade])?
    7. Materials
      1. How should future sign sheeting materials be implemented into the criteria?
      2. What is an actual expectation for the life of various sign materials (Note: It should be longer than the warranty periods)?
      3. Should the FHWA or another organization test sign sheeting materials to failure?
      4. How should changes in products be incorporated into expected service life values?

[1]Policy on Maintenance of Safety and Traffic Control Devices and Related Traffic Services. $1.50, available from the American Association of State Highway Officials, 917 National Press Building., Washington 4, D.C.

[2]This document is available for inspection and copying at the Federal Highway Administration, Office of Traffic Operations, HTO-21, Room 3419, 400 7th Street SW, Washington, D.C. 20510.

[3]This document is available for inspection and copying at the Federal Highway Administration, Office of Traffic Operations, HTO-21, Room 3419, 400 7th Street SW, Washington, D.C. 20510.

[4]SIA: Candelas per footcandle per square foot.

[5]CIL per unit area: Candelas per lux per square meter (Metric equivalent of SIA).

[6]Luminance: Foot-laberts (English), Candelas per square meter (Metric).

[7]Workshop Summary Memo, December 29, 1995

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