Breaking its conspicuous public silence on the World Trade Center redevelopment plan, the City Planning Department called yesterday for many changes that would open more of the streets, sidewalks and public spaces on the site.
One of the underlying principles is that streets work better when they are filled with cars and trucks. In contrast, pedestrian-only zones, which were once a favored device of planners, can sometimes seem lifeless.
"Vehicular traffic not only makes a street feel more public but more vibrant," said Amanda M. Burden, the director of the City Planning Department (the agency that administers planning) and the chairwoman of the City Planning Commission (the body that sets policy), which will consider the department's proposals next week. The commission's response may put the city administration at odds with state officials who control the process.
Ms. Burden said the department recommendations - building retail space immediately on all the commercial development parcels, moving a truck ramp, widening sidewalks and eliminating blank walls around the memorial - would "ensure that the World Trade Center site is reintegrated in every respect" with Lower Manhattan.
Parts of five city streets were closed in the 1960's to create the superblock from which the twin towers rose. The current plan developed by state officials calls for the recreation of Fulton and Greenwich Streets but not Washington Street, which run through the tower footprints. Dey and Cortlandt Streets are not shown as through streets on the latest plans.
Vishaan Chakrabarti, the director of the Planning Department's Manhattan office, told the commission yesterday, "First and foremost, we feel quite strongly that Dey and Cortlandt be extended through the site as real streets."
Vehicles pose an enormous security challenge in any high-profile setting, particularly one that was heavily damaged by a truck bomb long before it was devastated by airplanes.
"There is a security concern," said Joseph J. Seymour, executive director of the Port Authority of New York and New Jersey, which owns the trade center superblock.
He said planning principles were at issue, too. "We're looking more at enhancing public spaces and I'm not so sure vehicles do that," Mr. Seymour said. "But I'm confident that at the end of the day, we'll have worked out a consensus."
Mr. Seymour said that reopening Dey Street might affect the wedge-shaped plaza in front of the permanent PATH terminal, which is being designed by Santiago Calatrava. "Are vehicles something that would detract from that public space?" Mr. Seymour asked. He also said the authority did not want to make a commitment on reopening Cortlandt Street until the layout of surrounding retail space had been determined.
A key objection raised by Mr. Chakrabarti was to a truck ramp along Liberty Street. He said the protrusion of the ramp, combined with the elevated level of the memorial plaza, would turn the sidewalk between them into a "concrete channel."
Kevin M. Rampe, the president of the Lower Manhattan Development Corporation, said that solving this major design problem "is one of the things we're working on right now to be sure that we don't have that experience." And Mr. Seymour said the Port Authority would take a "second look" at the Liberty Street ramp.
Many of the city's positions were listed last October in a letter from Deputy Mayor Daniel L. Doctoroff to Mr. Seymour and Mr. Rampe.
What is significant about the commission's involvement now, as the general project plan makes its way through public review, is that it has "more than the power of positive persuasion," said David Karnovsky, the counsel to the Planning Department.
Should the planning commission formally recommend disapproval or modification of the plan, state law provides that the Lower Manhattan Development Corporation could override that only by a two-thirds vote of its board of directors. The corporation is expected to vote on the general project plan in May.
Ms. Burden said there had been a "fruitful collaboration" among city planners, the development corporation and the Port Authority but added, "Much remains to be done."
On parallel paths are the environmental review for the trade center site, separate reviews for the PATH station and the reconstruction of West Street-Route 9A, a federal historic preservation review and the development of design guidelines based on the master plan by Studio Daniel Libeskind. Mr. Rampe said the guidelines would address issues raised yesterday, like building setbacks and sidewalk widths.
Mr. Karnovsky told the planning commission members that "there is no memorandum of understanding or other instrument by which the Port Authority has committed itself to following this general project plan." But Mr. Seymour and Mr. Rampe said that such a memorandum would be signed once the plan was set.