The documents below contain technical information and guidance related to sign retroreflectivity.

• Maintaining Traffic Sign Retroreflectivity UPDATED IN 2013
  This 4-page technical brief provides additional information on the sign retroreflectivity maintenance requirements in the MUTCD. This document is referenced in Paragraph 4 of the 11th MUTCD Section 2A.22. [Publication No. FHWA-SA-07-020 (Revised 2013)]

• Methods for Maintaining Traffic Sign Retroreflectivity: [HTML, PDF]
  This 2007 report prepared by Texas Transportation Institute for the FHWA provides technical guidance on methods for maintaining traffic sign retroreflectivity in accordance with the new Federal rules. [Publication No. FHWA-HRT-08-026]

FHWA GUIDANCE MEMOS ON SIGN SHEETING PRODUCTS:

• Clarifying Guidance on Application of Daytime Luminance Factors in 23 CFR 655 [HTML, PDF]
  This January 2013 memorandum provides background and guidance on applying the regulations to newer sheeting types.

• Daytime Color Appearance of Retroreflective Traffic Control Sign Materials [HTML, PDF 1.15MB]
  This January 2013 memorandum provides background and guidance on applying the regulations to newer sheeting types.

• Recommended Minimum Maintained Retroreflectivity Levels for Blue and Brown Traffic Signs [HTML, PDF]
  This April 2012 FHWA memorandum provides information on minimum maintained retroreflectivity levels for white-on-blue signs and white on brown signs. These levels were established through research, but because they were not available during the rulemaking process, it remains the option of agencies to apply the values as the monitor, install and replace signs.

For information about traffic control devices and the Manual on Uniform Traffic Control Devices (MUTCD), other than visibility or retroreflectivity, please see FHWA's MUTCD website