Anyone who’s ever balanced a budget on any level — or, for that matter, mastered elementary mathematics — understands you can’t subtract a large number from a smaller number without ending up in the red.

Therein lies Washington States Ferries’ problem.

As the agency’s expense side continues to increase unabated — owing to everything from bloated union contracts for its employees to skyrocketing fuel costs and an antiquated, inefficient fleet of vessels — the income side of the ledger is limited to dipping into the state’s already overdrawn general  fund or transportation budgets.

Or raising fares.

Which brings us to the Washington State Transportation Commission’s recent recommendation to hike fares by 5.5 percent over the next 10 months.

That would include a standard 2.5 percent cost-of-living adjustment in October, followed by a 3 percent increase in May.

This comes on top of a 25-cent per ticket surcharge already being imposed to build a new 144-car boat.

On paper, a fare increase seems perfectly logical. But the real world doesn’t often translate to paper.

In this case, it’s hard to imagine commuters willingly embracing yet another assault on their pocketbooks.

At $15.20 for a car and driver, a trip from Bremerton to Seattle by ferry already costs more than the gas you’d burn driving around — plus the cost of a $2.75 toll to cross the Narrows Bridge.

And considering the voyage itself takes an hour, plus another half-hour waiting in line and however long it takes to drive to the ferry terminal, there’s no savings in time, either.

At this point, quite frankly, ferry travel is on the verge of becoming the plaything of tourists and those who relish the experience without fretting the cost rather than a practical, viable means of transportation for working commuters.

And since there aren’t enough of the former year-round to support it, you have to wonder at what point ferry service as we’ve come to know it will disappear entirely.