Clinton Seals Off Traffic From Part of Pennsylvania Ave. : White House: Street in front of executive mansion is permanently closed to vehicles. President calls it part of 11-step program to tighten security after terrorist attacks.

In a sobering sign of the times, President Clinton said Saturday that he had reluctantly ordered security officials to permanently close Pennsylvania Avenue in front of the White House to vehicular traffic as “a practical step to protect against the kind of attack we saw in Oklahoma City.”

The decision to restrict access to the well-traveled boulevard for the first time will inconvenience Washington residents and tourists. But the primary impact of the closing is its symbolic significance: The nation awoke Saturday to find concrete barricades sealing off one of the most famous stretches of what has been called “America’s Main Street.”

Officials said the two-block stretch will be converted into a pedestrian mall.

The rerouting of Pennsylvania Avenue traffic is the most dramatic element of an 11-part security program that has been adopted by the Administration. Other measures call for revisions in air-traffic rules to enhance security and improved coordination and emergency response by law enforcement agencies. The recommendations are the product of an eight-month review by the Secret Service, the Treasury Department and a specially appointed White House Security Advisory Committee.

“Clearly, this closing is necessary because of the changing nature and scope of the threat of terrorist actions,” Clinton said in his weekly radio address, which he devoted to the decision. “It should be seen as a responsible security step necessary to preserve our freedom, not part of a long-term restriction of our freedom.”

Officials involved with the review, which was launched after a stolen plane crash-landed on the White House’s South Lawn last Sept. 12, said the changes would have been approved even without the devastating April 19 truck bombing of the federal office building in Oklahoma City. But they acknowledged that the Oklahoma tragedy underscored the need to make sure that a car or truck carrying high-powered explosives cannot get close enough to the White House to inflict serious damage--a precaution the Secret Service has long advocated.

Anti-terrorism experts say that shortening the distance between an explosive device and its target increases the impact of a blast exponentially. The front door of the White House, which serves as both office and residence for the President and First Lady and contains offices for other senior officials, is about 100 yards from Pennsylvania Avenue; the distance to H Street, where traffic will be redirected, is several times that distance.

Clinton noted that Pennsylvania Avenue has remained open to vehicular traffic for 130 years, “through four presidential assassinations and eight unsuccessful attempts on the lives of presidents . . . through a civil war, two world wars and the Gulf War.”

The President had previously resisted suggestions to close the avenue. But in his radio address, he said it would have been irresponsible to ignore the advice of the Secret Service, “especially given the strong supporting voice of the expert panel.”

The advisory committee reviewed more than 1,000 documents and interviewed 250 individuals, including former presidents Gerald Ford, Jimmy Carter and George Bush, and experts from eight nations with considerable experience with terrorism. It drafted a top-secret, 500-page report with a 260-page appendix; Five of its 11 recommendations remain classified.

Despite his decision to authorize the security measures, the President exhorted the nation not “to be frightened or intimidated into a bunker mentality.” He said the White House will remain accessible to visitors through public tours, pedestrians and protesters can still gather outside the front gate, and the President will still be “every bit as active and in touch with ordinary American citizens as I have been since I took office.”

Some proposals were rejected by the advisory committee as too intrusive: establishing military-type checkpoints for vehicles driving in front of the White House on Pennsylvania Avenue, and screening pedestrians with metal detectors, said Ronald K. Noble, Treasury undersecretary for enforcement and chairman of the committee.

The panel’s mission became more urgent as it proceeded. In October, Francisco Martin Duran fired 29 rounds from a semiautomatic rifle into the White House from a point in front of the grounds. Four other incidents were reported in December.

Noble said in an interview that the key factors behind the decision were the White House’s proximity to Pennsylvania Avenue, widespread availability of unregulated materials that can be converted into explosive devices, easy access to bomb-making instructions, and “the overarching concern of the changing climate of domestic and international terrorism.”

Treasury Secretary Robert E. Rubin, whose domain includes the Secret Service, said he was persuaded of the need to improve White House security at an April 3 briefing. He discussed the matter with Clinton on Friday evening, at which time the President approved the security measures.

Officials said they rapidly closed off Pennsylvania Avenue to avoid encouraging a potential perpetrator to act before the closing was implemented. At 6 a.m. EDT Saturday, officials installed rows of concrete barricades and large concrete planters to seal off the two blocks between 15th and 17th streets that had been traversed by an average of 26,000 vehicles each weekday.

Officials said the design of the pedestrian mall and the designation of permanent alternate transportation routes will be addressed in the near future. Treasury officials said they will seek additional funds from Congress to carry out the plan, but would not disclose a cost estimate.

Despite the street closure, authorized vehicles will still have access to the White House on Pennsylvania Avenue, and the historic boulevard will continue to be used for inaugural parades.

On its first day as a vehicle-free walkway, the two-block stretch saw only a trickle of pedestrian traffic. Under clear, sunny skies, the six-lane span was strangely empty. A few residents and tourists took to the pavement on foot, bicycle and in-line skates. But most remained on the sidewalks, as though uncertain that they could safely venture onto the uncharted terrain.

Reaction to the closure was mixed. Several individuals complained of the inconvenience; others proclaimed themselves pleased to have a new car-free promenade in the heart of the city. Some said they understood the security need; others called it an overreaction--or even an effort to exploit public fear for political purposes.

“Most of them know why” it was done, said Philip Harris, who was selling sunglasses near the White House. “I think the concern is going to be the congestion.”

Several residents said the real test will come during rush hour Monday morning when commuters may find massive traffic tie-ups on an artery that links Washington’s busy downtown with Capitol Hill, many of the federal government’s offices and the Virginia suburbs.

Some were philosophical. Stanley Schmulewitz, a 25-year Washington resident, gleefully stood smack in the middle of the street gazing at the famous residence at 1600 Pennsylvania Ave. simply because he could. But he acknowledged the experience provoked mixed feelings.

“It just takes takes away from this being an organic part of the city, and isolates it more,” said Schmulewitz, an engineer with the Federal Communications Commission. “It’s letting the terrorists have their victory by changing our lifestyle.”

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White House Security

President Clinton has adopted recommendations to improve White House security. Six recommendations were made public; five others remain classified.

* Convert Pennsylvania Avenue into a pedestrian mall between Madison Place and 17th Street. Also, limit traffic behind the White House to pedestrians only.

* Discuss changes in air traffic rules to enhance White House security.

* Have the Secret Service, U.S. Park Service Police and Metropolitan Police Department, which share responsibility for safety in and around the White House, improve coordination.

* Create a forensic task force to respond to crises at the White House. The task force would include federal and local law enforcement agencies and fire, rescue and bomb squads.

* Improve communication among law enforcement agencies and White House security posts to ensure a prompt response to incidents.

* Coordinate Secret Service’s security measures.