OAKLAND (CBS SF) — Bay Area mayors trying to drum up support for a multi-billion dollar tax that will fund major upgrades on BART got on board the campaign train Thursday.

The mayors of the Bay Area’s three biggest cities – Oakland’s Libby Schaaf, San Jose’s Sam Liccardo and San Francisco’s Ed Lee – took a ride together on BART to campaign for Measure RR, on the ballot in November.

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The mayors said the measure on the November ballot comes at a critical time for BART and the future of Bay Area public transit.

BART is asking voters in Alameda, Contra Costa, and San Francisco counties for $3.5 billion to upgrade the aging system.

“It’s not sexy; it’s smart,” said Schaaf.

Measure RR is worth $3.5 billion in bonds paid for by property owners. If a house is worth $500,000, the homeowner would pay about 45 dollars a year every year until 2064.

It needs a two-thirds majority to pass.

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“If we don’t do this now, we’re going to put ourselves in great jeopardy, [in terms of] both the economy and livability,” said Lee.

While some voters are on board, others are mistrustful of the system.

“There is a lot of money coming at BART with the people that are commuting every day,” said Oakland resident Deandre Thrower.

Measure RR funds can only be used for infrastructure like replacing rails, modernizing BART’s train control systems and improving BART stations.

The San Jose Mayor Liccardo, whose citizens aren’t even voting on RR, said it needs to happen before BART’s planned move south.

It’s so critical that we fix it first, and measure RR ensures that we’ll have this viable backbone for our transit system for many decades to come,” said Liccardo.

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BART ridership is already often at capacity and is expected to increase by 75 percent by the year 2040.