NEW YORK--Planners seeking to rebuild the World Trade Center have always envisioned that the 16-acre site would have been a vibrant community with buildings, shops and cultural institutions lining a restored street grid, but the police department's latest security proposal entails heavy restrictions.

According to a 36-page presentation given by top-ranking police officials, the entire area would be placed within a security zone, in which only specially screened taxis, limousines and cars would be allowed through barriers staffed by police officers at each of the five entry points, The New York Times reported.

Roughly a dozen guard booths would be established at street corners where pedestrians or vehicles are most likely to enter the area, while the western lanes of Church Street would be reserved for emergency vehicles.

All service and delivery trucks for the trade center site would be directed to an underground bomb screening center at the south side of the complex. Tour buses would drop off and pick up passengers at Liberty and Greenwich Streets. But no bus would be summoned from the underground security center and garage until all the passengers are present, a requirement that could leave large clots of tourists waiting for stragglers.

The newspaper reported that the plan is designed to prevent a third terrorist attack on the site, said Paul J. Browne, deputy police commissioner for public information, and, he said, would have little effect on either traffic or pedestrians. It is among the more striking features of the police's overall plan for Manhattan security, which also includes measures to photograph every vehicle entering Manhattan, scan its license plate and keep the information on file for at least one month. The department hopes to have the plan in place by 2010, by the time Mayor Michael R. Bloomberg leaves office.

Landlords, company executives, public officials and some urban planners acknowledged the need for security at ground zero, but are worried that the procedures would undermine the effort to reweave the trade center site into the city's fabric. They fear that the proposed traffic restrictions could create tie-ups in a congested neighborhood and discourage corporate tenants from renting space, or shoppers from visiting the stores in the area.

Browne, addressing criticism that the security plan would undermine a normal commercial and cultural life in the neighborhood, told the newspaper, "I think this will reassure people that this is probably the safest business environment anywhere."

Browne said the plan, which is still being revised, would not involve checkpoints where pedestrians and visitors would have to open their bags for police inspection. "It's designed principally to prevent a car- or truck-bomb attack," he said, "but it's also been designed with traffic concerns in mind."

The proposal is part of the PD's Lower Manhattan Security Initiative, a version of which has been presented to agencies involved in rebuilding Lower Manhattan by Raymond W. Kelly, the police commissioner, and Richard A. Falkenrath, the deputy commissioner for counterterrorism. Like London's security cordon, known as the "ring of steel," the initiative relies on mobile teams of heavily armed officers as well as technology including closed-circuit television cameras, license plate readers and explosive trace detection systems.

But the trade center site plan involves a much higher degree of security.

Last month, the city and the Port Authority of New York and New Jersey, which owns the site, resolved a longstanding source of tension by giving Kelly and his department control over security at the complex. Under the plan, the department would establish a World Trade Center Unit with about 600 officers and develop the overall security plan.

"There is concern in the downtown business community that the security plans are going to make the logistics of doing business more difficult, everything from getting deliveries to moving clients and employees around," said Kathryn Wylde, president of the partnership. "Is it going to work, or make doing business and getting people downtown more difficult? I don't know."