CHICAGO (CBS) — The Regional Transportation Authority is beginning to worry about its ballooning backlog in funding from the state’s Public Transportation Fund — and what it could mean for CTA, Metra and Pace riders.

It doesn’t help that ridership on mass transit is down nationwide — the Chicago area’s loss of 4.5 percent is actually mild when compared with other big-city systems — or that the increase in state sales tax revenues is the smallest in six years. What’s really worrying RTA Executive Director Leanne Redden and her chief deputy, Jill Leary, is how badly the state has fallen behind — $484.5 million.

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Both said it’s a record. WBBM’s Bob Roberts reports.

The RTA has resorted to short-term borrowing to stay current in its subsidy payments to the three transit agencies.

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“We have maxed out our temporary short-term borrowing capacity,” Redden said.

CTA, Metra and Pace all have cash reserves, but the reserves are intended only as a stop-gap. Redden said all three agencies are looking at options that could include service cuts and fare hikes, which may be needed sometime in the coming quarter.

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CTA and Pace have in place 2017 budgets that did not cut service or raise fares; in fact, Pace has augmented service, particularly on its expressway and tollway corridor services. Metra raised fares in February, with the intention of setting aside the additional revenues generated to help pay the local share of federally-funded projects.