Frequently Asked Questions

  1. What are the current requirements for sign retroreflectivity?

    The 2009 Manual on Uniform Traffic Control Devices (MUTCD) Section 2A.08, Maintaining Minimum Retroreflectivity, is current. That Section did not change as a result of 2012 updates to the MUTCD. Only the compliance dates were revised.

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  2. Without compliance dates for replacing signs, when would signs identified through an agency‘s assessment or management method as not meeting the minimum retroreflectivity levels need to be replaced?

    Signs identified through an agency‘s method as below the minimum established retroreflectivity levels have exhausted their useful service life and need to be replaced because they do not meet the needed function of being adequately visible at night. Similar to other occurrences of signs that are no longer serviceable, agencies are expected to prioritize replacement of these signs based on engineering considerations such as the relative importance of the sign to the safety of the road user, volumes and speed of nighttime traffic, and optimal use of limited resources, among others. Signs that are no longer serviceable might demand a higher priority for replacement over other non-compliant signs that are replaced by systematic upgrading or routine maintenance schedules. Accordingly, it is expected that the use of the assessment or management method would serve to identify and program the replacement of signs that are found to or expected to be below the minimum retroreflectivity levels.

    Note: The compliance date of June 13, 2014 applies only to the implementation and continued use of an assessment or management method that is designed to maintain regulatory and warning sign retroreflectivity at or above the minimum retroreflectivity levels in Table 2A-3. Agencies are expected to add signs other than regulatory or warning to their method as resources allow.

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  3. What information is available to assist in the implementation of the new requirements for minimum sign retroreflectivity?

    The Federal Highway Administration (FHWA) developed training for Local/Tribal Technical Assistance Programs (LTAP/TTAP). LTAP and TTAP representatives who have received training will be able to assist highway officials comply with the provisions in the MUTCD regarding sign retroreflectivity. There are also several materials available on the Implementation Tools portion of this website:

    • Sign Retroreflectivity Guidebook “Toolkit”
    • Sheeting ID Guide
    • Informational and Training presentations

    Technical guidance and research materials are also available at the respective portions of this website. If you need additional information or have comments about the information contained, please contact your FHWA Division Office.

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  4. How can highway officials assure that they are meeting the new provisions for retroreflectivity and that their signs provide reasonable visibility at night?

    Since the retroreflective properties of traffic control devices deteriorate over time, highway officials should assess their schedules for inspecting, cleaning, and replacing signs to ensure that these maintenance activities meet the provisions of the MUTCD, and more importantly, the needs of drivers at night. Agencies will need to implement one or more of the five methods listed in the MUTCD to assess signs for nighttime visibility. These methods are described in detail in the Methods Report, or an agency may decide to develop its own assessment or management method that is tied to the minimum retroreflectivity levels in Table 2A-3 based on engineering studies. Additionally, procurement processes should be checked to ensure that sign materials are being specified that offer retroreflectivity performance that meets or exceeds the minimum levels specified in the MUTCD.

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  5. If I select the visual inspection method, is the only real requirement that my inspector be trained?

    No. There are three different procedures allowed for the visual inspection method, per FHWA’s “Maintaining Traffic Sign Retroreflectivity” which is referenced in the MUTCD. As required in the standard statement in Section 2A.08, each procedure has specific requirements to tie the procedure to the minimum values in Table 2A-3. Additional information on the methods is available in the Methods Report.

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  6. Can the retroreflectivity visual inspection method be performed using a nighttime photolog?

    Although work is progressing in this area, there is no known photo technology that can be used as a method to assess or manage sign retroreflectivity for the purposes of meeting the MUTCD retroreflectivity requirements at this time. Photography alone cannot represent actual retroreflectivity levels for signs in varying position, location, and retroreflectivity performance. To date, there is no technology that would enable camera logging to be accurate and repeatable for meeting the MUTCD requirements.

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  7. Why are signs with blue or brown backgrounds excluded from these retroreflectivity requirements?

    At the time that the rulemaking to add sign retroreflectivity requirements to the MUTCD occurred, the research for signs with blue or brown backgrounds had not yet been completed. However, a research report (Publication No. FHWA-HRT-08-029) that provides minimum recommended retroreflectivity levels for blue and brown signs is now available as well as a guidance memorandum.

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  8. Can I use any type of sign sheeting as long as its retroreflectivity meets the minimum specified levels?

    Table 2A-3 indicates that any type of sheeting including the Type I (commonly called Engineering Grade), Type II (commonly called Super Engineering Grade), or Type III beaded (commonly called High Intensity Beaded) sheeting and the Type III, IV, VI, VII, VIII, IX, or X prismatic sheeting may be used on any sign with the following exceptions: Types I, II, and III beaded sheeting cannot be used for the white legends on overhead guide signs; Type I beaded sheeting cannot be used for the white legends on ground-mounted guide signs; and Type I beaded sheeting cannot be used for the yellow or orange backgrounds on warning and temporary traffic control signs.

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  9. Can I still use Type I Engineering Grade sign sheeting?

    Type I Engineering Grade sign sheeting may still be used for white, green, and red backgrounds. Type I Engineering Grade sign sheeting also may still be used for the white legend on a sign with a red background. Thus, STOP signs and black-on-white regulatory signs may still be made from Type I Engineering Grade sign sheeting.

    However, when agencies review their signing practices and their choice of sign materials, the annualized costs of the signs using factors such as expected sign life should be considered. Even though a particular type of sheeting might initially meet the minimum retroreflectivity levels when it is new, it might quickly degrade to below the minimum retroreflectivity levels, thus losing its effectiveness at night and requiring replacement the next time its retroreflectivity is assessed. The use of higher performance sheeting, even though it has a higher initial cost, might provide a better life-cycle cost for the agency.

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  10. What sheeting should I use for my agency?

    Cost increases from upgrading materials and/or processes might be offset by the long-term savings that result from the longer life of the higher performance sheeting products.

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  11. Table 2A-3 indicates that ASTM Type III white beaded sheeting cannot be used for overhead signs. If existing overhead signs are lighted, is Type III allowed?

    Per Section 2A.07 of the MUTCD, if a sign is illuminated it does not have to meet the minimum retroreflectivity levels, However, if the agency turns the sign lighting off at times, the sheeting should meet the minimums.

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  12. What are the minimum values for fluorescent colors?

    Fluorescent yellow and fluorescent yellow-green signs need to meet the minimum retroreflectivity levels for yellow signs, and fluorescent orange signs need to meet the minimum retroreflectivity levels for orange signs.

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  13. Why are different numbers shown for green on overhead signs? For example, Type I = 7, Type II = 15 and Type III = 25. If 7 is sufficient for Type I why wouldn't it be the minimum level for all other types? On the other hand, if 25 is the minimum for Type III how can 7 be acceptable for Type I?

    For any specific real-road scenario, a specific sign luminance is needed. That luminance is associated with a non-standard retro geometry (something other than 0.2 degrees measured on retroreflectometers). At that non-standard geometry, all the materials must produce the same minimum retro value. However, each type of sheeting has different observation angle-retroreflective curves because of their different optics. To transform retroreflectivity from the non-standard geometry to standard geometry, it must be done for each sheeting type along that sheeting’s specific observation angle curve. When the transformation is completed, the differences in some materials are enough that they need to have different minimum retro levels at the standard geometry of alpha = 0.2.

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  14. Is there a sign inventory program available for local agencies to use?

    Local agencies are encouraged to check with their Local Technical Assistance Program (LTAP) Center. If the local LTAP Center does not have a sign inventory program, they can obtain a generic inventory program from one of the other LTAP Centers in the country.

    Several State DOTs have also been very active in assisting local agencies with sign retroreflectivity. If agencies do not have a contact person at their DOT, they can contact the local FHWA Division Office for assistance.

    There are also proprietary inventory software programs available. They are often very good, but can also be expensive. It is helpful to find one that will work for your agency now and well into the future.

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  15. What is retroreflectivity?

    Retroreflectivity is a term that is synonymous with the coefficient of retroreflectance, which is formally defined in ASTM E808. In general terms, retroreflectivity describes the efficiency of a material to redirect light back to its source. This is a unique form of the more common diffuse reflection, whereby light is scattered in all directions after striking an object. Retroreflective materials are engineered to redirect most of the light back toward the source, which gives signs and pavement markings a brighter appearance at night from the driver’s perspective.

    Motorists experience the benefits of retroreflectivity whenever light from their headlights shines on traffic signs. Signs made with retroreflective sheeting materials appear to glow in the dark, making them easier to see. The legends on retroreflective signs provide important information to motorists as they navigate the nation’s highways, streets, and roads at night.

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  16. What makes the traffic signs visible at night?

    Traffic signs are covered with retroreflective sheeting materials. These materials are usually made with tiny glass beads embedded in plastic or with a very small, complex pattern of cube corners that work like prisms. Both of these types of retroreflective materials redirect light back towards its source, but the performance of the materials varies. Photographs of various sheeting patterns of both types are shown on the Retroreflective Sheeting Identification Guide produced by FHWA.

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  17. Why is the FHWA concerned about the visibility of traffic signs at night?

    One of the FHWA’s primary missions is to improve safety on the nation’s roadways. On average, 40,000 men, women, and children have been killed annually on American roads over the past decade. While only one quarter of all travel occurs at night, about half of the traffic fatalities occur during nighttime hours.

    One of the primary reasons for this disparity is the lack of visual cues that indicate roadway curvature or other critical information to the driver. During daylight hours, visual cues include such things as shoulders, pavement markings, overhead and post-mounted signs, roadside vegetation, guardrails, fences, and buildings, which make navigation easier. At night, the driver must rely on overhead or sign lighting (when available) and the small amount of light that the headlamps provide. At typical highway speeds, headlamps provide very little illumination at the distances drivers need to make decisions. Retroreflective materials extend the capabilities of the headlamps, making the critical visual cues provided by signs, pavement markings, and delineators visible at much greater distances.

    While signs and markings installed by agencies typically have good retroreflective properties when they are installed, their performance degrades over time due to exposure. Adequately maintained retroreflective signs are critical to meeting the driver’s visibility needs at night because they heighten motorists’ understanding of the roadway, enhance traffic flow, and have the potential to improve highway safety. Nighttime visibility of traffic control devices is becoming increasingly important as our population ages. By the year 2020, about one-fifth of the U.S. population will be 65 years of age or older. In general, older individuals have declining vision and slower reaction times. Signs that are easier to see and read at night can help older drivers retain their freedom of mobility and remain independent.

    The recommendations and requirements for the retroreflectivity and/or illumination of signs at night are included in the MUTCD.

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  18. What is the MUTCD?

    The Manual on Uniform Traffic Control Devices (MUTCD), which is published by the FHWA, defines the standards used by road managers nationwide to install and maintain traffic control devices on all streets and highways. The MUTCD is available at: http://mutcd.fhwa.dot.gov.

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  19. Why are requirements for sign retroreflectivity included in the MUTCD?

    Section 2A.07 of the 2009 MUTCD states, “Regulatory, warning, and guide signs and object markers shall be retroreflective or illuminated to show the same shape and similar color by both day and night, unless otherwise provided in the text discussion in this Manual for a particular sign or group of signs.” This standard has remained essentially unchanged for over 50 years. The MUTCD also says in Section 2A.22, “To assure adequate maintenance, a schedule for inspecting (both day and night), cleaning, and replacing signs, gates, and object markers should be established.” This statement has also been in the MUTCD for quite some time.

    Further impetus for attention to sign visibility resulted from the 1993 U.S. DOT Appropriations Act requiring the Secretary of Transportation to “…include a standard for minimum level of retroreflectivity that must be maintained for traffic signs and pavement markings for all roads open to public travel.” In response to this legislative mandate and after many years of research and proposed rulemaking, the FHWA has developed and adopted a set of minimum retroreflectivity levels for traffic signs.

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Program Contact

Cathy Satterfield

What's New

FHWA Resource Charts, July 2013

FHWA Roadway Lighting Handbook, August 2012

RwD Strategic Plan, April 2013

Updated Guidance on Sign Retroreflectivity, April 2013

Clarifying Guidance on Daytime Luminance, January 2013

Guidance for the Selection , Use and Maintenance of Cable Barrier Systems, November 2012