September 22nd, 2011
SIGN UPDATEUncategorized, by Catherine Higgins.
Interstate signs are updated to improve safety and provide better readability and directional help for road users.
New signs have been placed on Interstate 15 near Cedar City. The signs meet new Federal standards and the messages on the signs have better relevance to the local area.
As interstate signs age and Federal standards change, UDOT identifies interstate segments that could be improved by a sign facelift. Sometimes single signs need to be replaced due to fading or other damage, but replacing a sequential group, as exemplified by the Cedar City project, gives UDOT the chance to update a series of signs that work together to provide clarity and consistency for road users.
Evaluation of old signs is based many factors. Current Federal standards are outlined in the Manual on Uniform Traffic Control Devices (MUTCD). Here are three broad areas engineers consider when prioritizing sign replacement projects:
Retroreflectivity: Light that bounces back to a light source instead of being generally diffused is retroreflective. “It’s right back at you,” says Wes Starkenburg, Sign Engineer at UDOT. Signs use sheeting and tape with prismatic reflectors that send headlight beams back to drivers.
Federal requirements determine the level of reflectivity of all signs on roads with public access. The level of retroreflectivity is evaluated by a trained sign inspector who visually inspects sings. Wear from weather and sun can decrease the level of retroreflectivity making signs harder to read. A trained eye taking a look at signs at night is a good start. Using a retroreflectometer allows an objective evaluation.
According to FHWA, approximately three times as many crashes occur at night, making retroreflectivity of signs an important safety feature.
Readability: Lettering used on interstate signs, sometimes informally called “Highway Gothic” is simple and easy to read. Spaces between letters, the shape and size of lettering are consistent from sign to sign which helps avoid confusion. The number of words should be limited so signs can be read quickly.
Messaging: As cities grow and small towns become more urban, messages on signs can become outdated. To make sure a series of signs helpful to road users, UDOT works with local elected or transportation officials to develop new messages to provides good directional help.