New York City is throwing away its welcome mat.

Mayor Michael Bloomberg has proposed a new $8-a-day tax for the privilege of driving into Manhattan (unless you stay north of 86th street).

For trucks, it’s even worse: $21 a day.

The mayor calls it a “congestion fee.” In fact, it’s a tax and a penalty for using a motor vehicle. The revenue would go to mass transit, not to roads and bridges.

City officials across America are watching to see whether Bloomberg can push it through — because plenty of those cities have worse traffic congestion than the Big Apple, according to the leading national study.

Los Angeles, San Francisco, Washington, D.C., Atlanta, Houston, Dallas-Fort Worth, Chicago, Detroit, Miami, Boston, Orlando, San Diego and Baltimore are just some of the areas with worse congestion, determined by the annual benchmark study done by Texas A&M University.

Might entry fees be proposed to get drive into the core areas of those communities? And would they match New York’s audacity on how to spend the money?

Instead of using it to improve the roads and bridges used by drivers, Bloomberg each year would transfer hundreds of millions of dollars paid by drivers into financing more mass transit, which is already heavily subsidized by drivers and the general taxpayer. Overall, the plan would help support about a $50-billion expansion of NYC’s huge transit system.

The plan hopes to capitalize on the media’s efforts to stampede the public into fear of global warming; it’s touted as environmental protection, hoping to disguise its true nature as a major new tax.

Mayor Bloomberg’s Earth Day-timed announcement featured a video introduction by California Gov. Arnold Schwarzenegger, the West Coast’s Rockefeller Republican. That raises obvious questions of whether the “Governator” is ready to test similar ideas in California. British Prime Minister Tony Blair also made a video appearance, claiming a similar plan is working in London, and saying “This would mark out New York as a global leader in halting climate change.”

Because the NYC plan would require an intricate, Big-Brother monitoring system to track each vehicle’s movements, just building the high-tech infrastructure is estimated to cost an initial $225 million, and the federal government is already being suggested as the source for that money.

The Bush administration’s Transportation Secretary Mary Peters didn’t throw cold water on the notion. “This plan is the kind of bold thinking leaders across the country need to embrace if we hope to win the battle against traffic congestion,” she responded. Fortunately, that’s all the secretary said, leaving plenty of wiggle room.

Rising fuel prices already provide free-market disincentives for drivers, but if they switch to mass transit, there will be fewer drivers left to subsidize that transit — thus the $8-per-day fee to make up the difference and keep the subsidies growing.

We’re already hearing angry outcries from those who would be hurt by this fee. But imagine the even larger outcry if Mayor Bloomberg had proposed funding the mass-transit expansion by raising the fares on the subway and buses.

What’s called the “farebox recovery rate” covers about half the New York system’s annual operating costs — and none of the capital expenses — leading to an annual deficit in the billion-dollar neighborhood. Even so, riders there pay a larger share than in any other transit system in America. The average system recovers about 25 percent of its operating expense from fares, but none of its capital costs. And New York’s mass transit users wouldn’t be the ones paying for this $50-billion capital expansion.

Traffic congestion is a serious problem. The U.S. Transportation Department has suggested various approaches that include “value pricing,” whereby users of toll roads would pay higher rates during peak periods.

However, true value pricing typically would use the extra fees to improve roads and bridges to handle the traffic. Bloomberg’s proposal instead would take the money paid by autos and trucks and send it to further subsidize mass transit.

Usually overlooked in transportation debates is the fact that automobile users already pay a heavy government burden for daring to favor the freedom and flexibility that automobiles provide. One-sixth of the federal fuel taxes paid by drivers already is being diverted to mass transit.

The request for federal funds guarantees this proposal will stay in the national spotlight. If New York gets the money, other cities will want it, too. As the song “New York, New York!” proclaims, if you can make it there, you can make it anywhere.

Ernest Istook is a visiting fellow at The Heritage Foundation (heritage.org). As a former U.S. congressman, he chaired the Appropriations Transportation Subcommittee, which decides federal funding for America’s transportation systems.