BRENTWOOD -- Far East Contra Costa commuters may actually have something to look forward to Monday.

Friday was the last weekday that eastbound drivers would be stuck at the traffic signal at Sand Creek Road and Highway 4, which has caused gridlock for years.

The final touches were made Friday to shift traffic on the freeway to new lanes so that starting Saturday morning, a freeway bridge will cross over the road, and drivers can use offramps to exit at Sand Creek.

Overlooking a line of traffic on Highway 4 that extended more than a mile north to Lone Tree Way, local elected leaders and transportation officials gathered on the new bridge Friday afternoon to mark what they called a "milestone" in the $37 million project.

"I'm jacked up. This is a big deal, not just for Brentwood, but for all of East Contra Costa County," said Brentwood Mayor Bob Taylor. "It will serve drivers for a much wider area and really open things up."

The gridlock often backed drivers up for miles, especially during the afternoon rush hour, leaving them two blocks from home but forced to wait 15 to 20 minutes to make a left turn, he said.

"This provides a huge value and improves the quality of life for many residents, to get home to their families," said county Supervisor Mary Nejedly Piepho, of Discovery Bay.

Taylor added: "Instead of going 5 (mph), drivers can go 55."

The two-lane road has also caused safety concerns.

State Assemblywoman Joan Buchanan, D-San Ramon, said her office had "numerous" clippings of crashes on the road, while her district director, Iris Obregon, feared letting her daughters drive that road at night.

"This is not only going to help people get home, but make it much safer," she said.

Engineers at Friday's event said the project contractor would be adding the "final touches" for the switch overnight, including adding safety barrier rail, striping and sign placement at Sand Creek.

When completed by the end of next year, Highway 4 will have onramps and offramps at Sand Creek and four lanes from Lone Tree south of Sand Creek.

A full traffic alignment switch, which would include moving westbound Highway 4 traffic off the traffic signal, is scheduled for late October.

Recently, officials shuffled money around to add construction of a second bridge overcrossing at Sand Creek, allowing the point on the freeway where traffic funnels from four lanes to two to move about a mile to the south, near San Jose Avenue.

Work is being done to incorporate the second bridge design into the project. Adding dirt embankments for the overcrossing could start by late October, officials said.

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