PLEASANTON -- With a first Bay Area toll lane proving it can help traffic congestion, freeway managers are planning for another on the same stretch of road from Milpitas to Pleasanton.

The first express lane opened there on southbound Interstate 680 in September 2010. Since then one opened in Santa Clara County, and plans are now underway to add a northbound toll lane along the Milpitas to Pleasanton route.

Don't expect a quick arrival, though, of the new 14-mile-long express lane between Silicon Valley jobs and East Bay suburbs. It could cost roughly between $170 million and $280 million.

It could take until 2018 to build, wire and open the brand new lane, freeway managers said in a meeting Wednesday night in Pleasanton on environmental planning for the project. It would be open to carpools for free and to solo drivers for an electronic toll that varies with congestion.

Caltrans, the Alameda County Transportation Commission and the Santa Clara Valley Transportation Authority are teaming up with the CHP to plan the new lane.

The southbound I-680 toll lane charges tolls between 30 cents and $7.50 per trip.

"The express lanes are an important tool to decrease congestion overall and improve the reliability of travel time for those in lane," said Art Dao, the Alameda County commission's executive director. "We need to squeeze all the efficiency we can get out of our existing freeways because we're not in a position to build new ones in the Bay Area."

Dao said the new I-680 toll lane could be finished perhaps two years or three years earlier than 2018 if Alameda County voters on Nov. 6 pass the Measure B1 sales tax increase, which earmarks $60 million for the project.

That money -- coupled with $20 million already set aside -- would provide a base to seek state, federal and regional funding officials said.

Planners had hoped the southbound express lane would generate surplus income to fund other new lanes, but that hasn't happened so far.

Funding isn't the only project issue to be determined.

Planners are doing studies to determine if the future northbound toll lane should be designed differently than the existing southbound lane to ease commuter complaints about too few entrances and exits.

The southbound toll lane has only three entrances and three separate exits on its entire 14-mile length from Highway 84 in Pleasanton to Highway 237 in Milpitas.

Some commuters grumble that so few is inconvenient.

Planners will consider at least three options for more and different types of lane exits and entrances. But allowing people to zip in and out of the lane too often could increase risks of collisions, said Kanda Raj, the ACTA express lane project manager.

"We want to provide good access to the lanes, but we need to make sure it's safe," he said.

Drivers using the southbound I-680 express reach their destinations an average of three minutes faster than those in the regular lanes, he said.

While three minutes may not sound impressive, the regular lane users sometimes get delayed 30 minutes when stuck in traffic jams that express lane users miss. "The express lanes provide predictable travel times," Raj said.

Toll lane use has increased 25 percent in the last year, up to 2,250 drivers per weekday in September.

Contact Denis Cuff at 925-943-8267. Follow him at Twitter.com/deniscuff

WHERE i-680 TOLL LANE USERS LIVE
Cities with the most users of the I-680 toll lane (from September 2010 through Feb. 24, 2012)
1) Pleasanton: 17,573
2) San Ramon: 13,590
3) Livermore: 10,736
4) San Jose: 10,334
5) Dublin: 8,829
6) Fremont: 5,501
7) Danville: 4,817
8) Walnut Creek: 4,549
9) Tracy: 4,031
10) Concord: 3,943
11) Oakland: 2,368
12) Castro Valley: 2,256
13) Alamo: 2,023
14) Lafayette: 1,919
To view more information on I-680 toll lanes, visit www.680expresslane.org/
Source: Alameda County Transportation Commission