In promoting his sweeping traffic reduction plan, Mayor Michael R. Bloomberg and his aides have stressed one provision: drivers who enter Manhattan below 86th Street would be charged an $8 fee.

But what has not been widely mentioned is a measure that could startle some Manhattanites: those who live within the zone would have to pay $8 to drive out.

The congestion pricing program was devised to cut traffic, chiefly by persuading people from the other boroughs and beyond to leave their cars behind and take public transit into Manhattan. But planners say that those who live inside the congestion pricing zone also contribute to traffic when they drive out, and should pay their share, too.

That means a man from Greenwich Village who drives to visit his grandmother in Queens would pay the fee. So would a C.E.O. who has a reverse commute, driving from the East Side to Stamford, Conn., each morning, and an Upper Eastsider who likes to drive to the Fairway supermarket in Harlem.

It might seem that anyone taking a car out of the congestion zone ought to be rewarded instead of penalized, but officials disagreed.

"We're not trying to get people to leave the zone in their cars," said Deputy Mayor Daniel L. Doctoroff, who played a leading role in fashioning the plan. "Overall what we're trying to do is get people to use their cars less."

By Danny Hakim

New York City could start charging residents to park in their own neighborhoods under Mayor Michael R. Bloomberg's congestion pricing plan. The mayor's proposal, which was introduced in the State Senate this month, would charge most drivers $8 to enter Manhattan below 86th Street on weekdays. To mollify people just outside the zone who feared their streets would turn into parking lots, the Senate bill would allow the city to issue permits so that most parking spots would be restricted to neighborhood residents.

But the bill says there would be unspecified fees that residents would have to pay to get those permits. The money would go to the city's general fund.

John Gallagher, a spokesman for the mayor, said "discussion of a fee structure for residential permit parking is very premature." Among other details of the plan, visitors coming into the city could deduct the cost of bridge and tunnel tolls from an $8 fee to enter Manhattan, but only if they use E-ZPass. And the state's environmental review process would be waived to speed up the plan.

We took a dive into the fine print of the mayor's proposal. As one might expect with such a voluminous piece of legislation, a number of notable items emerge from the fine print.

It's not spelled out how visitors driving into New York City would be made aware that they had to pay $8 within 48 hours or face a $115 fine. The mayor and his administration have said most people would likely have heard about the congestion fee, though some lawmakers say many might not. The mayor's staff says there would also be adequate signage. Lawmakers have wondered how this would actually work: The signs, presumably, would have to explain how and where to pay, requiring a lot more words than "toll ahead."

ALBANY, June 7 - Mayor Michael R. Bloomberg's plan to reduce traffic by charging people who drive into the busiest parts of Manhattan received significant support on Thursday as Gov. Eliot Spitzer endorsed the idea and the Bush administration indicated that New York stood to gain hundreds of millions of dollars if the plan were enacted.

If the measure is approved by the Legislature, New York will become the first city in the United States to impose a broad system of congestion pricing, which was introduced in London in 2003 and has been credited with reducing traffic there.

Governor Spitzer said he would work to ensure passage of the plan, which is a major part of the mayor's blueprint for improving air quality and traffic flow for the next several decades. The Bloomberg administration has estimated that it could put the program into effect within 18 months of legislative approval.

"This is a necessary investment for the future of New York City, which is to a great extent the economic engine of New York State," the governor said. "And so this is not really a question of whether, it's a question of how, it's a question of making sure that we do it properly."

Mr. Spitzer appeared alongside the United States transportation secretary, Mary E. Peters, who announced that New York City was one of nine finalists for a share of $1.1 billion in federal aid to fight urban traffic. Ms. Peters warned, however, that the city's potential share could be endangered if the mayor's plan did not have state approval by August.

FOR the small group of economists and policy wonks interested in applying supply-and-demand theories to the thorny problems of gridlock and ever-longer commutes, the $2.9 trillion fiscal 2008 budget released by President Bush on Monday contained some excellent news: $130 million in grants to finance construction of so-called congestion pricing systems.

Congestion pricing - the concept of charging higher fees to consumers for a good or a service at times of heavy use - is well established in businesses like hotels, long-distance phone service and air travel. And while London and Stockholm have successfully enacted plans that levy fees on drivers who want to enter traffic-clogged city streets, the United States has been slow to apply the concept on the roads. When Mayor Michael R. Bloomberg proposed last year that New York look into congestion pricing as a means of unclogging the city's famously clogged roadways, he was roundly criticized.

Actually, congestion pricing was born and bred in New York City. William Vickrey, the longtime Columbia University economist and 1996 Nobel laureate, is viewed as the father of the concept. In 1959, long before E-ZPass was a twinkle in a planner's eye, Mr. Vickrey proposed that cities could reduce traffic by using electronic systems to charge drivers for the privilege of nosing their sedans into urban grids.