Drivers on Interstate 77 in York County may think they’re seeing double, but their eyes aren’t playing any tricks.
The duplicate road signage is part of a S.C. Department of Transportation interstate sign upgrade replacement project.
The Federal Highway Administration requires states to have replacement plans for signage. South Carolina uses the accepted useful life of the reflective property of the signs’ sheeting as a base for its replacement programs, said SCDOT District 4 construction engineer Melanie Mobley.
“The time span is 12 to 15 years,” she said. “Even though they look good during the day, if you look at them at night you’ll see a remarkable difference in the reflectivity of the signs. It’s a mandate by the Federal Highway Administration that we replace them on a regular basis.”
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The project is specific to York County. Each county is on a different cycle to cause less traffic disruptions within the same year.
Mobley said once the new sign has been installed, technically, the old sign can be removed. But the process is a bit more complicated because the signs are barcoded and Geolocated with GPS coordinates.
“A private contractor is doing the work, but they have to coordinate with our maintenance office so they can get the new signs barcoded and GPS located,” she said. “That’s how the maintenance department keeps up with the signs all over the county.”
Installation began in July. Although Mobley hopes the project is completed by spring, she’s uncertain due to a utility conflict with the locations of two overhead signs. She said she doesn’t know how long it will take for the utilities to be relocated because SCDOT has no authority over the utility companies.
“Usually when we have a utility conflict we can move the sign 10 feet further in one way or the other,” she said. “But with these two signs, there’s a tight window of where it can go. So we can’t avoid the utility.”
Wet weather conditions also have slowed the project. Many signs, especially the overhead signs, are posted in a foundation of concrete which requires a certain amount of dry time to cure and gain full strength. Mobley said this is a time-consuming, front-end effort.
“I know to the general eye it looks like we’re just putting up the exact same signs and they look very similar,” she said. “But there is an established useful life for the reflectivity of the sheeting on those signs, it deteriorates over time.”