As it stumbles through the coronavirus pandemic, Caltrain still has ambitious plans to electrify and nearly double the size of its fleet by 2022. All the agency needs is money.

So officials are taking steps to put a ⅛-cent sales tax on the November ballot in San Francisco, San Mateo and Santa Clara counties. The proposed tax got a go-ahead from San Mateo County Transit District Board of Directors on Wednesday, though it still needs approval from the boards of Muni, Valley Transportation Authority and Caltrain, as well as all three county Boards of Supervisors.

Charles Stone, a board director for SamTrans and Caltrain, said he understands the idea may seem, well, aspirational, at a time when the world is collapsing under a global pandemic, and Bay Area residents are all but imprisoned in their homes. Ticket sales for Caltrain dropped 95% on the first day of the regional shelter-in-place order. Since then they’ve hovered at 86% below normal levels.

Caltrain relies on fares to cover 70% of its operating costs.

“Sure, it’s really easy to say, ‘How could you even think about revenue measures right now?’” Stone said. “But at some point this crisis is going to be over, and we’re going to return to the world we lived in before.”

He said he’d like to inhabit a world that retains the few bright spots of the pandemic — light traffic on freeways and clean, refreshing air. A more robust Peninsula transit system that runs on electricity would help serve those goals.

If passed, the measure would generate $100 million in badly needed cash per year, which Caltrain would use to convert its existing diesel trains to electric cars, and expand service from 92 trains a day to 168 trains a day by 2022.

Executive staff at Caltrain put together a long-range “service vision” last year, which aimed to triple the number of riders on the rail system — from 60,000 a day to 180,000 — while swapping the diesel-belching locomotives for 10-car electric trains that would arrive at stations every 7½ minutes. That vision would accommodate a booming population, drawn to new housing and tech campuses along Highway 101. It came with a hefty price tag: $25 billion.

But at the time, the Bay Area’s transportation future looked promising. Business leaders and advocates were campaigning for a “Faster Bay Area” mega-sales-tax measure — also primed for November — that would fund a variety of projects, possibly including the extension of Caltrain into downtown San Francisco. It died last month, as the coronavirus diverted policymakers’ attention to more pressing emergencies.

Stone now feels lucky that Caltrain continued pursuing its own measure in parallel, just in case Faster Bay Area didn’t work out.

Still, his fellow SamTrans board member, San Mateo County Supervisor Dave Pine, saw little hope of even getting a sales-tax measure on the ballot — let alone winning support from two-thirds of voters in three counties.

“We understand that the potential for going forward with a tax measure is very small,” Pine said. “But we also know that Caltrain faces a fiscal cliff if it doesn’t obtain a dedicated source of revenue.”

That was true even before the coronavirus battered Caltrain and other mass transit systems. If the rail system substantially beefs up its service and infrastructure by 2022, it could face a substantial operating deficit by 2023.

Rachel Swan is a San Francisco Chronicle staff writer. Email: rswan@sfchronicle.com Twitter: @rachelswan