DANVILLE -- Commuters driving on Interstate 680 can expect a little faster and safer travel through Danville and San Ramon soon with the opening of new merging lanes along two miles of freeway.
The $34.3 million auxiliary lane project will make it easier to merge into and out of the traffic flow when entering or exiting I-680 between Sycamore Valley Road in Danville and Crow Canyon Road in San Ramon, engineers said.
In a low-key debut, the northbound merging lane will open to traffic early Friday and the southbound lane early on July 1.
The lanes function like runways, giving entering and exiting motorists a longer stretch of asphalt to ease in and out of traffic without forcing other drivers to brake as sharply.
"The extra space in the lanes allows cars to move in a more predictable way that is safer," said Susan Miller, director of projects for the Contra Costa Transportation Authority. "That reduced friction to the flow allows everyone to move along a little faster."
The transportation authority and Caltrans partnered in overseeing the project, the last of three phases of $54.4 million in auxiliary lanes on I-680 between Diablo Road in Danville and Bollinger Canyon Road in San Ramon.
The three phases together will save I-680 motorists an estimated average of about two minutes during the rush hour.
Danville officials predict local traffic benefits as well. They said the lanes will make it less tempting for motorists to cut through town as a detour to avoid freeway congestion.
Danville drivers also can use the merging lanes for a quick freeway trip between the two ends of town, said Newell Arnerich, a Danville city councilman and member of the transportation authority commission.
Transportation managers say the project will make the freeway more efficient in an era with less state and federal dollars to widen entire freeways.
The federal government provided $21.2 million for the project, while Tri-Valley developer fees provided $10.9 million. The state chipped in $1 million, and the county half-cent transportation sales tax provided $1.2 million.
The auxiliary lanes were among the original projects envisioned when Contra Costa voters approved a transportation sales tax in 1988.
Landscaping along the two miles of freeway will come later this year.
The landscaping appeared to be uncertain earlier this year when Gov. Jerry Brown imposed a moratorium on new freeway landscaping in areas with severe water shortages during the drought.
Caltrans, however, recently approved the I-680 landscaping. The project is located within the East Bay Municipal Utility District, which has not declared water shortages severe enough to warrant drought rates.
The completion of the project also means the approaching end of periodic nighttime lane closures, which have slowed freeway travel.
Even after the lanes are open, however, some nighttime lane closures may be required until late July while contractors finish up some median work.
The merging lane project comes with an artistic accent. Decorative oak leaves were added at Danville's request to a retaining wall beneath the Greenbrook Drive freeway overcrossing. The town's emblem is an oak tree.
Contact Denis Cuff at 925-943-8267. Follow him at Twitter.com/deniscuff.