The California Highway Patrol and the state’s department of transportation have begun testing a new system that alerts drivers against hazardous fog conditions on roads.

The system uses a network of visibility sensors and traffic sensors to provide real-time information to the drivers about foggy conditions on roads.

The technology is being tested under a $12m pilot programme on a 12-mile stretch of Highway 99 south of Fowler, which faces the notorious Tule fog, using six weather stations, 22 visibility sensors and 41 traffic sensors.

Information from the sensors and stations will be fed to 39 electronic message signs along the highway to be monitored at the transport department’s traffic management centre.

On registering a visibility of less than 500 feet, the sensors will alert drivers through message boards against foggy conditions and at less than 200 feet, drivers will be warned against dense fog.

Fog is statistically the worst weather condition for driving and November traditionally marks the onset of fog season, according to California state transport officials.