The last standing piece of the World Trade Center towers -- a seven-story twisted metal ruin that has come to symbolize the terrorist attacks -- was torn down Tuesday and saved for possible use in a memorial.

"We're going to preserve as much of that wall as possible," Mayor Rudolph Giuliani said before workers attached cables to the structure and began bringing it to the ground. "We may be doing a memorial with some or part of that wall."

The remnants of the south tower -- the one struck by the second jetliner and the first to collapse -- have been captured in scores of photos of ground zero since the Sept. 11 attack on the twin 110-story towers.

Amanda Gallaghre, a Manhattan tour guide, was one of several people watching near the site as the last chunk of the building came down. She was supposed to lead a tour of the trade center on the afternoon of the attack.

The metal wall "should be part of a memorial, so it can stand as a lasting memory to all the people who died there," she said.

Removal of the tower will also make cleanup efforts safer and easier, the mayor said.

Earlier, as New Yorkers voted in primaries for his replacement, Giuliani encouraged residents to get on with life.

"Life is risky," he said. "You can decide to live your life afraid of that happening, or you can decide to live your life the way Americans live their lives, which is unafraid. There's no reason to have this increased fear."

Giuliani's comments came as workers started a third week of digging through the ruins of the twin towers and as the families of the more than 6,000 victims began receiving help in paying their bills.

The mayor cited statistics showing that violent crime has plunged in the two weeks since the terrorist attack. New York is now the safest large city in America, the mayor said.

The attack on the trade center was "a once-in-our-history incident," Giuliani said.

The mayor also said a regulation is being considered to bar single-occupant passenger cars from entering the city to cut down on traffic, beginning Thursday.

The plan at this point would ban all single-occupant passenger cars heading into Manhattan at the four East River bridges below 59th Street -- the Queensboro, Williamsburg, Manhattan and Brooklyn bridges.

The city was considering extending the ban to the Queens Midtown Tunnel and the Lincoln Tunnel. The ban would run between 6 a.m. and noon.

A Wednesday morning meeting between the mayor and city transportation officials will formulate the final plan. The decision followed a Tuesday morning traffic jam that Giuliani described as horrible.

Preserving the ruined tower as a memorial was suggested by Philippe de Montebello, director of the Metropolitan Museum of Art, and by John Tierney in his column Tuesday in The New York Times, saying: "It's the building hanging on, still refusing to fall, just like New Yorkers."

In Oklahoma City, granite salvaged from the bombed Alfred P. Murrah federal building in 1995 was used in a memorial to the 168 victims. Also, Berlin, London and Hiroshima have erected monuments from wartime debris.

Giuliani, who is barred from running for a third term, discouraged New Yorkers from casting a write-in vote for him. But he has left the door open to trying to extend his stay at City Hall to oversee the city's recovery.

Many New Yorkers, enamored with Giuliani's performance following the Sept. 11 attack, seemed inclined to keep the mayor in office for a third term.

"It's a bad time to train a new mayor," said Douglas Green, voting in a temporary polling site for lower Manhattan residents displaced by the attack. "We need someone with experience to lead us in this time of crisis."

The number of confirmed dead at the trade center rose Tuesday to 287 as the number of missing dropped to 6,347. Giuliani said the numbers are likely to change. Of the confirmed dead, 224 had been identified. Only five survivors have been found -- none since the day after the attack.

The Red Cross announced that it has sent out its first batch of payments to the victims' families to help them with short-term expenses such as mortgages, rent or funeral costs.

The organization will give grants of up to $30,000 to families of those who died or are reported missing in the attacks on the twin towers and the Pentagon. The first checks were sent Friday.

On Wednesday, the city will provide free legal assistance to families so that they can quickly and more easily collect death benefits and get access to bank accounts without having to produce a body.