According to the reporting of Charles V. Bagli, in the NYTimes:
the entire area would be placed within a security zone, in which only specially screened taxis, limousines and cars would be allowed through ‘’sally ports,'’ or barriers staffed by police officers, constructed at each of five entry points.
The proposal threatens to reopen a bitter debate that many had thought was settled four years ago.
Landlords, company executives, public officials and some urban planners acknowledged the need for security at ground zero, but 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.