UDOT signs may soon be more retroreflective.
Gone are the days when all freeway signs require active lighting to be seen at night. The sheeting material used to face modern signs is highly retroreflective — meaning the light bounces off of the sign right back to the light source. Many freeway signs don’t need active lighting due to the high level of retroreflectivity of sign materials.
UDOT requires that signs be faced with retroreflective Type 9 sheeting. New Type 11 sheeting, which has a higher level of retroreflectivity, can be used. Contractors who bid for UDOT projects can select the most appropriate sheeting for the job.
UDOT uses active lighting on all system to system interchanges and other places where the roadway is complicated or the signs use a lot of text. For example, the I-15 to I-80 interchange in Salt Lake County has active lighting to assist state-to-state motorists. For other locations, UDOT uses active lighting on a case-by-case basis. Motorists who observe lighting fixtures that may not be working as intended should call 801-975-4000 to report the location.
Retroreflectivity on signs can be diminished over time due to weather, vandalism or other damage. Ongoing evaluation of signs, especially those that have been in place for several years, is important to maintaining safety on UDOT facilities. At UDOT, maintenance workers conduct inspections as part of an overall plan to make sure signs meet new federal standards.
Visual inspection at night is critical when evaluating how effectively retroreflective signs are doing their job. Signs with small areas of damage may be readable during the day, but “the effect of that damage at night could be huge” says UDOT Operations Design Engineer Wes Starkenburg. For example, a paint ball hit can prevent the reflective material from shining in headlights.
A retroreflectometer can be used to take objective measurements. Several measuring devices are available – some require actual contact with the material being measured.
When signs get too old, worn or damaged, single signs are replaced, but typically UDOT identifies interstate segments where a series of signs could be improved. Replacing signs in a segment gives UDOT the chance to update signs that work together to provide clarity and consistency for road users.
UDOT uses materials that have been tested by ASTM International, an organization that tests products to set standards for many industries. Sheeting materials are tested in a lab that’s set up to approximate how road users will see signs at night with headlights. Testers evaluate sheeting attributes including color, gloss, opacity, and texture, and take objective measurements.