Motorists in Paso Robles should expect significant delays on a major thoroughfare for about a month while Pacific Gas & Electric Co. upgrades its circuit system.

Work on South River Road between Niblick and Creston roads begins Wednesday and is slated to last through mid-April, according to a news release from the city.

Construction crews with the utility will flag traffic daily as they restrict the two-lane road to one lane. The city advises motorists to plan alternate routes.