Traffic on the Harbor Freeway in downtown Los Angeles. (Photo: Jose Luis Stephens, via Shutterstock)

Keeping roads pothole free has been a challenge in California for decades.

But an unusual solution has emerged — a per-mile-driven fee on motorists, called a Road Use Charge, with the money going to build and maintain infrastructure, including roads and highways.

Four years ago, the state authorized a little-known pilot program for the Road Use Charge, or RUC, and 5,000 motorists participated