Imagine gliding from Walnut Creek to Mountain View at rush hour without getting stuck in traffic or settling in for a ride to San Francisco International Airport from the North Bay knowing you won’t have to get up from your seat to make a transfer.

That’s the vision behind a multibillion-dollar idea to ease commute times and reshape transportation in the Bay Area over the next several decades.

Called the Bay Area Regional Express Transit Network, or ReX, the concept from transportation think-tank TransForm seeks to get commuters out of their cars by knitting together the region with next-generation buses that travel on an extensive network of dedicated lanes to ensure they don’t get bogged down in traffic.

The group’s idea is an ambitious attempt to realize a pair of goals among transit officials: creating a Bay Area equivalent of the express bus systems that zip past traffic in cities around the world, and providing ways for people to move more seamlessly across a region with more than two-dozen transit agencies.

“It is a big vision for how to get transit in the Bay Area to work better for more people,” TransForm spokeswoman Edie Irons said.

TransForm is submitting the concept to the Metropolitan Transportation Commission as one of several big-picture projects meant to anticipate the transportation solutions the Bay Area will need over the next several decades. On Thursday, the group publicly unveiled its concept and a proposed map for the system.

The price tag for all this: $12.6 billion to $17.5 billion, according to TransForm’s estimates. If the Bay Area embraces the concept, Irons said, the system could be in place within 10 to 15 years.

Leaders say funding for the system could come from a proposed one-cent sales tax measure that local transportation advocates hope to put on the ballot in November 2020, which would raise $100 billion over four decades for region-wide transit projects.

Public transportation advocates said the ReX concept could draw drivers out of their cars and fill in the gaps between the Bay Area’s often-disconnected transit systems. Gwendolyn Litvak, a senior vice president for transportation policy at the Bay Area Council — one of the transit and business organizations leading the campaign for the sales tax measure — applauded the idea.

“People don’t just stay in their hometowns. We know that people move across the entire Bay Area,” Litvak said. “We would like to see more projects like this.”

In TransForm’s vision, ReX would blur the lines between bus and rail travel — riders would board long, electric buses that arrive every few minutes at attractive “hub” stations, which also would house food stands and shops.

The vehicles would run on a massive expansion of the express lane network that is already in place on some Bay Area freeways but that is crucially without connections in several places and does not include traffic-choked bridges.

Under ReX, those express lanes would ring the bay and run across all of the region’s bridges. Even if cars are stuck in traffic, the thinking goes, unimpeded buses could cruise by at no less than 45 miles per hour.

And they wouldn’t be contained to freeways — perhaps the boldest piece of TransForm’s idea is its call to create miles of new tunnels and fly-overs through parts of San Francisco, San Jose and other dense urban areas that would take buses out of the roadway entirely.

“People don’t have much incentive to take transit when transit is stuck in the same traffic as everybody else,” Irons said. “The idea is to get transit out of traffic as much as possible.”

The ReX vehicles would make few stops between each of the hub stations, allowing people to move quickly from city to city. Local “link” routes with more frequent stops would pick passengers up at the stations and take them closer to their final destinations.

Stops also would serve as connections to existing transit systems such as BART, Caltrain and VTA.

Some aspects of TransForm’s concept are likely to raise eyebrows as more people seek affordable housing at and beyond the edges of the Bay Area, however.

In TransForm’s map, express bus lines would not extend south of Diridon Station, leaving out much of San Jose as well as Morgan Hill and Gilroy. The main lines wouldn’t reach eastern Contra Costa and Alameda counties either, where studies show residents have some of the worst commutes in the Bay Area. The same goes for nearly all of Solano County and all of Napa and Sonoma counties.

Meanwhile, the group calls for tunneling under the length of Berkeley’s College Avenue and down Broadway in Oakland to create a new roadway for its buses — an expensive proposition that would essentially duplicate service already provided by BART lines not far from the route.

TransForm Regional Policy Director Chris Lepe noted that BART trains into San Francisco already are packed at rush hour, which he said would only get worse as the Bay Area grows in years to come.

“Imagine looking out to 2050 — what that demand is going to look like?” Lepe said.

Metropolitan Transportation Commission officials will spend the next several weeks evaluating the ReX proposal and others like it to see how they could benefit the Bay Area and where they could be improved. Lepe said TransForm expects to revise the ReX concept over time with that feedback.

“This is a first iteration,” he said.