Here comes a whopping taxi-fare hike.

Under a proposal by the New York Taxi Workers Alliance — the cabdrivers union — the price of an average three-mile, evening rush-hour trip would increase by 15 to 20 percent.

A typical trip price would go from $10.80 to $12.30, with “clicks” — for every fifth of a mile — rising from 40 to 50 cents.

Other potential hikes include costs for airport trips, creation of a morning surcharge and an increase in the evening one.

Officially, the Taxi and Limousine Commission will discuss proposals at a Thursday hearing. But it seems the fix is already in for higher fares this summer.

TLC head David Yassky signaled as much last week: Citing higher gas prices, he told a City Council committee, “I think the proposals to increase the fare are appropriate.”

Mayor Bloomberg called it “a good idea.” He, of course, has alternative means of transportation (like helicopters).

But that doesn’t make him wrong.

There hasn’t been an across-the-board fare increase since 2006 — and while there may be a harder-working, more deserving-of-a-raise group than New York’s cabbies, none comes to mind.

What’s problematic, frankly, is the notion of a cab-drivers union in the first place.

The NYTWA was recognized by the AFL-CIO last year, and now it’s looking to make its bones.

Technically an association of independent contractors, the NYTWA is seemingly learning from Big Labor’s public-sector brethren, like the UFT and TWU.

It is, in effect, unionizing a public utility, demanding that government — the TLC — exercise its coercive powers on behalf of union members.

This won’t immediately yield the benefits that teachers and transit employees enjoy, but that will come in time — beginning when the union succeeds in bribing a sufficient number of City Council members.

Already enjoying undue influence with the council are the fleet owners and their million-dollar taxi medallions — an intrinsically unsympathetic bunch who are pushing a proposal of their own.

They want to hike fares by 20 percent, but also raise the daily leasing fees paid by cabbies — effectively absorbing whatever fare increases the drivers win.

That, frankly, should be a nonstarter.

The medallions, after all, add no value to the equation — they are simply a tool for enforcing and extending a monopoly that benefits owners, but not drivers or the general public.

In a perfect world, anyone with a clean driving record could declare himself a hack and begin charging whatever he wished for a ride. The market would sort things out fast enough.

In the real world, things are more complicated.

One result is New York’s over-regulated system — a thoroughly warped market that makes for obscenely expensive medallions, fixed-price fares, frustrated drivers and a powerless public.

The newly aggressive union is just going to make things worse.