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."