Safety Matters: Sign Visibility and Retroreflectivity

safety_matters_logo Sign Visibility and Retroreflectivity 

Every day, no matter where we go or what we do, we see signs. Whether it’s the STOP sign at the end of a street, a pedestrian warning sign or the sign directing you to the beach, all of the signs we see are regulated by the Federal Highway Administration’s Manual on Uniform Traffic Control Devices (MUTCD). The size, shape, color and messaging are all specified in the MUTCD and allow for a person to travel from a small rural community in Connecticut to a city like Los Angeles, CA and recognize each and every sign. This is most important when it concerns traffic control signs – it would be nearly impossible to move around safely if regulatory signs weren’t uniform!

Almost as important as their uniformity is their visibility. A sign can only provide information to the roadway users if those users can see it. The MUTCD has the following language with regard to sign design and retroreflectivity.


Some visibility issues are easy to identify and resolve. A low-hanging branch that blocks a sign can be identified and cut rather quickly. A sign that has been vandalized can be repaired or replaced. More difficult, though, is determining if a sign is no longer retroreflective. During the day, a sign may look worn, but does that make it no longer retroreflective at night? Since Public Works crews work during the daytime, it can be hard to conduct proper nighttime visual inspections of signs. Ensuring that the proper signs are installed and maintained has a measurable impact on roadway safety. Signs that are visible in the day provide information to drivers but may be one of many visual cues to aid the driver in their decision making. At night, when many of those other cues may not be visible, signs become even more important.


  • Daytime
  • Many cues available 
  • Driver task relatively easy




  • Nighttime 
  • Few cues remain
  • Task more difficult



A sign inventory is an effective way to keep track of the life of signs, which aids in assessing their retroreflectivity. Using an established method to assess and/or manage regulatory and warning signs for retroreflectivity is also an FHWA requirement. The different ways that sign retroreflectivity can be determined are listed below:

  • nighttime visual inspections using comparison panels
  • nighttime visual inspections using calibration method
  • nighttime visual inspections using consistent parameter method
  • measured using retroreflectometer

Many local agencies do not have the ability to bring staff in at night to conduct visual inspections. Another option is to anticipate the expected life of a sign and replace signs on a rotating basis, but this can be costly if signs are needlessly removed. A retroreflectometer can be used during the day and provides an objective measurement; however, they are cost prohibitive for most local agencies. The T2 Center does have two retroreflectometers, as part of the Equipment Loan Program, which can be borrowed by a municipality to conduct sign inspections. More information can be found on our website by clicking here.

Maintaining sign visibility is an important and necessary part of keeping our roadways safe for all users. The better the information is that we provide, the easier it is for the driver to complete the task needed to navigate the road.

Additional information on retroreflectivity requirements can be found in the MUTCD and on FHWA’s website at:

For more information and assistance with local road safety in your community, contact Melissa Evans, Safety Circuit Rider, at


About Connecticut T2 Center

The Training & Technical Assistance Center at UCONN provides education and technical assistance to members of Connecticut's Transportation and Public Safety Community, including municipal public works directors, street and road maintenance superintendents and staff, city and town engineers, Connecticut Department of Transportation employees, transportation planners and law enforcement professionals serving as legal traffic authorities. We are Connecticut's LTAP Center
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