Cambridge's Architects Collaborative has proposed a split-level pedestrian walkway which would leap-frog the streets and buildings of Harvard Square.

H. Morse Payne, a member of the design team, said that the TAC project, first announced last May, hinges on the legal and financial cooperation of the dozen property-owner whose buildings the walkway would adjoin. Speaking at the First Parish Church in Cambridge yesterday, he said that with some exceptions, the businessmen have as yet offered no firm commitment.

The Collaborative has estimated the total cost of the walkway at $823,000. Further expenses, such as new construction at the second level and new store-fronts for existing buildings, could cost in additional $1,800,000.

Funds would have to come from the property-owners. Payne admitted, in return for which they would receive "in creased rents from the leasing of the new retail space" on the second level. He said he hoped for a "gesture of interest" from the city-possibly financing construction over public rights-of-way, or merely furnishing "legal sympathy" in such matters as zoning.

Cambridge city councillor Cornelia Wheeler, present at the meeting, said she felt "much enthusiasm" for the plan, and criticized the Harvard Businessmen's Association for what she called its "apathetic, content" attitude.

Payne said that each of the 12 property-owners had been approached individually, and that the Collaborative anticipates "no negative response." He said he hopes for a joint meeting of TAC representatives with all 12 "within a month or two."

Aimed at enhancing the "shopping experience" for Harvard Square pedestrians, the proposed split-level walkway would stretch from the Yard to Mt. Auburn St., weaving in and around the buildings of the Square in such a way that "a whole new level of activity is created, undivided by streams of vehicular traffic," as described by the TAC proposal.

Payne, who taught at the Graduate School of Design until 1963, spoke of the walkway web as "tame, non-aggressive" redevelopment, contrasting it with massive, "visionary" schemes such as those proposed by the Cambridge Redevelopment Authority and "Team Monad," a group of former GSD students.

"Our plan is intimate," he explained. "It's magical and fun-like. Architectural differences seem to be part of it, unordered and unregimented."

As detailed by the TAC proposal, "The activities envisioned along the walkways would be essentially related to the cosmopolitan types of people who are attracted to the Square," and would feature assorted shops, boutiques, cafes, and galleries, "and possibly bistros and a small theater."

Payne's presentation Sunday showed "before and after" views of Square scenes to dramatize what he called the "urban excitement" of the proposed changes.