Express lanes on the Interstate 680 just north of Pleasanton are nearing completion, scheduled to open in early fall, though a hard date has not yet been specified.

The project converting carpool lanes into toll express lanes is intended to promote carpooling and improve traffic congestion on the I-680 corridor, Metropolitan Transportation Commission (MTC) project manager Barbara Laurenson said at the San Ramon City Council meeting Tuesday night.

"We're doing this for mobility," she said. "As the region grows, we need to have an infrastructure that is supportive of carpools, vanpools and express buses. We all are suffering from the growth of our region, and we know that we have to use all the tools that we have to reduce congestion."

The project includes one northbound express lane from Alcosta Boulevard in San Ramon to Livorna Road in Alamo, and one southbound express lane from Rudgear Road in Walnut Creek to Alcosta Boulevard. It's part of a larger plan sponsored by MTC and the California Department of Transportation (Caltrans) to develop an integrated Bay Area express lanes network.

The $45 million project involves converting high-occupancy vehicle (HOV) lanes into toll express lanes. Project construction, which began in August 2015 and was initially expected to be completed in late 2016, is now scheduled to be completed by late September or early October, Laurenson said.

Everyone can drive in the lanes, but only HOV and some select others can use them for free during toll hours -- similar to the express lanes on I-580 through the Tri-Valley and I-680 south of Pleasanton.

In order to use the express lanes, drivers will need to obtain a toll tag -- toll-exempt vehicles must use a FasTrak Flex toll tag, set in the "2" position for 2-person carpools and the "3+" position for everything else, while solo drivers can have either a standard FasTrak toll tag or a FasTrak Flex tag set in the "1" position.

Solo drivers will be charged a toll fee to use the lanes, while carpools, vanpools, eligible clean-air vehicles, motorcycles and buses can use the lanes toll-free.

The lanes will operate from 5 a.m. to 8 p.m. weekdays and will be managed and monitored by MTC.

A key component of the plan, said Laurensen, is "dynamic tolling" -- as traffic increases, tolls increase, and vice versa.

The minimum toll price will be $0.50 and the maximum toll will be set by supply and demand. There may be times, said Laurenson, during which the lane will be "open to all."

There are two zones in each direction, and the pricing signs along the freeway will specify how much solo drivers will end up paying to reach the end of the zone versus the end of the express lane. For example, a driver heading north from Dublin may be tolled $1 to reach Crow Canyon Road (the end of one zone) and $3 to reach Livorna Road (the end of the express lane).

"A driver is guaranteed the price shown on the sign at the time the driver enters the express lane," MTC officials wrote in a staff report. "If the toll amount changes while the driver is in the lane, the driver still pays the price posted when entering the lane."

Lane enforcement will look similar to that across Bay Area bridges. Cameras are present to snap photos of license plates, and when someone travels on the express lane with the FasTrak Flex tag set in the "2" or "3+" position, said Laurenson, that will "trigger a beacon on the express lanes, which will let the CHP (California Highway Patrol) know to extra look at that car to ensure that it is 2 or 3-plus."

"A lot of the revenues from the tolls goes to pay extra CHP officers to be out there and looking at the lanes," she added.

Those who drive on the lanes without the proper FasTrak tag will be charged violation fees, starting at $25 and escalating up to $70.

At Tuesday's meeting, Laurenson acknowledged counter arguments that have been raised to express lanes in general.

Some say the toll tag requirement is an unfair burden, she said, while others state that allowing single-occupant vehicles actually slows the lane down, and is an example of the government prioritizing revenue over mobility. But, said Laurensen, the dynamic tolling is MTC's response to deal with that potential.

Another critique has been one of inequity, that the express lanes are unfair to low-income drivers who may not be able to afford the toll to beat traffic. Laurenson responded to that as well, stating that nationwide research has shown that drivers of all income levels use the express lanes.

Councilman Scott Perkins suggested that staff consider that the lanes be open to all from 10 a.m. to 2 p.m., while Councilman Harry Sachs raised the concern that metering lights would be implemented next, something that he feels is a problem in Fremont.

"For San Ramon, I want to know what the plan is for metering lights, if there is any," Sachs said, "so that we can be able to forecast this and figure out what's the best strategy given what we have here and what we're looking for in our infrastructure vision."

Laurenson closed her presentation by going over public outreach plans, including online ad campaigns and the MTC mailing list.

"As a 40-something-year-old mom, I don't use Twitter," Laurenson said. "But I'm all over NextDoor. So we're using a combination of those different tools."