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As more people crowd the Bay Area, jostling for jobs in Silicon Valley and San Francisco and converging on already-congested freeways, the Peninsula’s commuter railroad is looking to grow, transforming a once-sleepy suburban line into a truly urban transit system.

Caltrain’s vision contemplates BART-like “show-up and go” service, whisking passengers from San Francisco to Gilroy on trains that run at least every 15 minutes all day long. The agency presented its vision — and accompanying business plan — for the first time publicly in a YouTube town hall event Monday, with more public meetings rolling out over the next several months before the agency’s governing board officially adopts the plan.

It’s a huge step for the agency, said Laura Tolkoff, a policy director with SPUR, an urban planning think-tank.

“This business plan is a big deal,” Tolkoff said. “It would really move Caltrain from an infrequent, ephemeral, commuter-focused service to an outstanding transit system that serves many different people for many different kinds of trips.”

Gone would be the days of passengers organizing their lives around the train’s schedule, as Millbrae resident Emily Sontag does every day on her commute to and from work, she said. She often stays late at her Stanford job, not leaving until around 7 p.m., at a time when Caltrain runs only once an hour. If her bus hits too many red lights or gets delayed for any reason, she said, she’s stuck waiting at the station.

“And that sucks,” Sontag said, adding that more service “would be wonderful.”

“It would definitely make my commute way easier and take away the stress of timing those connections,” she said. “And it might make it easier to take the train for things like going out to dinner or catching a movie when I would otherwise take Lyft.”

Like Sontag, three-quarters of Caltrain’s passengers are “choice riders,” said Seamus Murphy, a spokesman for the agency, meaning they have the option of driving or taking some other form of transportation. By increasing the number of trains from five to eight during the peak hour and running express Baby Bullet trains every 15 minutes, Caltrain expects to nearly triple the number of riders, from around 65,000 per day today to 180,000.

That’s the equivalent of adding five and a half lanes to the freeway without any of the carbon-spewing side effects, Murphy said.

The Peninsula — and the Bay Area as a whole — will need the added people-moving capacity as it continues to grow, said Matt Quevedo, the director of housing, transportation and community engagement for the Silicon Valley Leadership Group, a business advocacy organization. Over the next 20 years, regional planners estimate the Bay Area’s population is expected to increase by more than 40 percent, adding 2.4 million residents and 1.3 million jobs.

“We need this corridor moving to keep our local economy moving,” Quevedo said, adding that if the plan is approved, it would help move more people up and down the Peninsula. “Commuters who don’t take the train will see less traffic congestion, better air quality and better commute times.”

But it won’t be cheap. To run more trains and add more passengers, Caltrain anticipates it will need around $90 million per year in operating subsidies, in addition to state funds and revenue from fares, the latter of which covers about 70 percent of its operating budget.

To help raise those funds, Caltrain has floated the idea of increasing the sales tax in San Francisco, San Mateo and Santa Clara counties by either one-eighth or one-quarter of one cent, generating around $100 million or $200 million annually, respectively, for operating costs, capital projects and other needs. If it does decide to ask for the sales tax increase, it would place the measure on the 2020 ballot, said Sebastian Petty, Caltrain’s director of policy development.

There’s also been talk over the past several years of a $100 billion or more regional transportation funding measure, that could include a mix of property, sales and business taxes, with the goal of better knitting the region’s more than two dozen transit agencies into a cohesive, high performing and high ridership system, and Caltrain may try to seek funding through that measure, Petty said.

If Caltrain is to realize its dream of becoming a truly urban transit system, it will need to do much more than add trains and run them more often, he added; it will need to integrate its service with others planned for the region.

There’s a proposal to add train service across the Dumbarton rail corridor, to the Monterey peninsula, and across the San Francisco Bay in a new transbay tube. There’s planning underway to extend Caltrain’s line in downtown San Francisco from its terminus at 4th and King streets to the Salesforce Transit Center and to build a new world-class train depot at Diridon Station in San Jose.

“We wanted to articulate a complete or end-state vision,” Petty said, “so we could really show what a fully complete system looks like.”

All of those capital projects — not including a second Transbay Tube or other rail services — are estimated to cost around $25 billion, of which roughly $6.5 billion would be needed for improvements solely related to increased Caltrain service, such as adding grade separations and passing tracks or lengthening station platforms.

But it won’t need to do all of that work before it can start running a few more trains, said Jim Hartnett, Caltrain’s general manager. More than $2 billion in improvements to electrify Caltrain’s diesel-powered line and add 19 new electric trains is already underway and expected to be complete by 2022.

The electric trains, which will replace most of Caltrain’s current fleet, stop and start more quickly than the diesel trains, speeding up the trip. And the agency will be able to run one more train during the peak commute hour, Murphy said, for a total of six trains in both directions, which the agency expects will encourage around 20 percent more riders to start taking the train. More improvements to service can be added incrementally, Hartnett said.

But while increasing the number of peak hour trains from five to eight is a significant step, some transit advocates say the agency could aim even higher. Caltrain’s business plan contemplates a scenario where 16 trains could run during the peak hour, nearly quadrupling the current ridership and sharing the tracks with not only high-speed rail but other train services, such as the Altamont Corridor Express or the new Dumbarton rail, as well.

The region is only going to continue to grow, said Adina Levin, the co-founder of Friends of Caltrain, a transit advocacy organization. So why not aim high, she said, even if the vision isn’t ultimately achieved due to factors outside of Caltrain’s control, such as the fate of high-speed rail.

“We understand Caltrain staff might be feeling a little cautious and are thinking they should under-promise,” Levin said. “But what we want to see from Caltrain is to say, ‘Our goal is to aim high and we will do what we can to surmount any challenges that come up.’ We think that will set the direction and position people with the right mindset to do just that.”