BRENTWOOD -- Preparation work is underway for shifting Highway 4 traffic onto a new configuration.

As part of that construction, realignment work is being done this weekend on the existing on- and offramps at Lone Tree Way, according to a Contra Costa Transportation Authority news release.

Flaggers will be at the ramps to enforce traffic control from 9 p.m. Friday to 7 a.m. Saturday and midnight to 7 a.m. Sunday, ensuring safety for workers and the public.

The Lone Tree off ramp will be closed from 11 p.m. Friday to 2 a.m. Saturday.

Work will include placing traffic control devices, safety barrier rails, striping and signs, transportation officials said.

Additionally, a single lane of eastbound Highway 4 will be closed from Laurel Road to Lone Tree from 9 p.m. Friday to 2 a.m. Saturday.

Motorists are advised expect delays.

Highway 4 traffic through Brentwood is expected to shift onto the new alignment in late September, at which point there will be no more three-way traffic stops at Sand Creek Road.

For construction updates, visit www.4eastcounty.org.

Contact Paul Burgarino at 925-779-7164. Follow him at Twitter.com/paulburgarino.