A correction to an earlier version of this article has been appended to the end of the article.

DANVILLE — All systems are go for the far left lanes on Interstate 680 between Walnut Creek and San Ramon to switch from carpool lanes to express lanes on Oct. 9.

The Metropolitan Transportation Commission announced this week the conversion of what for several years have been carpool lanes into express lanes, where solo drivers can elect to pay a toll for the privilege to drive faster at some of the busiest times of the day and week. That toll varies based on real-time traffic conditions; the more traffic there is, the more it will cost.

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Traffic on major Bay Area freeways has grown 80 percent since 2010 Before paying that premium, Joe Thomas of Walnut Creek wants to see how well the high rollers roll.

“I’ll hold back a few weeks and see if it makes a difference,” said Thomas, who drives alone daily from his Walnut Creek home to his Danville job. That 6-mile run on 680 may, or may not, be worth spending 50 cents — or several dollars at peak times — to get into the fast lane, he said.

It is based on the idea that solo drivers paying to use the fast lane will reduce congestion in the other lanes.

“It’s a matter of trying to squeeze more efficiency out of the right-of-way that already exists,” said John Goodwin, a spokesman for the MTC, which will administer this newest stretch of express lanes.

Drivers using the express lanes in Contra Costa and elsewhere — even if they are carpools, motorcycles, buses or other vehicles that can use the lane for free — must use a properly mounted FasTrak transponder, or FasTrakFlex transponder set to “1” for solo drivers or “2” or “3+” for vehicles with more than one occupant, Goodwin said.

The southbound I-680 Contra Costa Express Lane starts at Rudgear Road in Walnut Creek and ends at Alcosta Boulevard in San Ramon, a 12-mile stretch.

The northbound Express Lane begins just south of Alcosta Boulevard extending 11 miles to Livorna Road in Alamo. There are two “zones” in each direction, with the Crow Canyon Road interchange being the dividing point.

The pricing — anywhere from 50 cents per zone on up — will be in effect from 5 a.m. to 8 p.m. Monday through Friday.

While there’s no maximum charge per zone, at peak traffic times — northbound I-680 between 4:30 and 5:30 p.m., for instance — solo drivers won’t be allowed in the express lane at any price, Goodwin said.

These are Contra Costa’s first express lanes. There already are two stretches in Alameda County — Interstate 580 between Greenville Road in Livermore and the junction with I-680, about 12 miles; and I-680 between Highway 84 near Sunol and Highway 237 in Milpitas, which opened in 2011. There are other express lanes in Santa Clara County, on about 5 miles of Highway 237 (and a short distance north from that on I-880) in Santa Clara County.

Does giving solo drivers access to the carpool lanes help move traffic? The answer seems to depend on which road you’re talking about, and when. The Alameda County Transportation Commission said early grades for the I-580 stretch have been favorable, showing traffic moving 10 mph faster in the express lane than in the other lanes. Reports about I-680 on the Sunol Grade have been less positive.

And no miracles are promised; Goodwin said that, during the busiest commute times, “the express lanes are not going to move the needle much, in all candor.”

The endgame, Goodwin said, is to have by 2035 express lanes along all Interstate highway routes, and certain other commute routes, enabling long commute trips to save 15 to 20 minutes a trip by maintaining an average speed of 45 mph. Toll money goes not only to maintaining the present infrastructure, he said, but to building future lanes.

Jessica Geddes of Walnut Creek, who like Thomas commutes each weekday to Danville, said she doesn’t plan on ever paying.

“I’m frustrated with the change,” said Geddes, who is dismayed by the longer hours for travel restrictions (all day, vs. commute hours for carpool times).

Goodwin agreed not everyone will love the new system. “One is not obliged to enter the express lane,” he said.

Correction: An earlier version of this story incorrectly reported that the FasTrakFlex transponder must be set on “1” for carpools and other vehicles allowed in that lane for free. The correct settings should be “1” for solo drivers on that stretch of highway and “2” or “3+” for vehicles with more than one occupant.