Supporters of building a bicycle and walking path across the Verrazano-Narrows Bridge are gathering tomorrow in Bay Ridge to rally for the project. The MTA released a preliminary report this week evaluating the prospects for a path, and it depicts a more complex undertaking than many advocates expected. The advocates working for walking and biking access on the bridge aren’t deterred and say the fact that the MTA is taking the idea seriously is a major step in the right direction.

The Verrazano Bridge opened in 1964 without bicycle and pedestrian access, an oversight that advocates have been trying to correct for a long time. In 1997, the Department of City Planning hired Ammann & Whitney, the firm that designed the bridge, to study the feasibility of adding a bikeway [PDF]. Since the bridge is controlled by the MTA, the city’s report largely sat on a shelf since its release nearly two decades ago.

More recently, a coalition of advocates renewed the push for a Verrazano-Narrows path under the banner of the “Harbor Ring,” a loop of connected bike paths around Upper New York Bay.

After advocates earned endorsements from elected officials, last year the MTA hired consultant WSP Parsons Brinckerhoff for its own feasibility analysis. On Tuesday, the authority briefed advocates and the press on the preliminary results of the study [PDF].

The document examines three options: Building paths on each side of the bridge’s lower deck, a similar plan on both sides of the upper deck, and a new, lower crossing parallel to the existing bridge. The new span would have a vertical lift to allow ships to enter the harbor.

The most complex part of the project is on the Brooklyn side, where the bridge paths would descend to ground level and connect with the popular greenway in Shore Park. The bicycle path, on the north side of the bridge, would follow a long, swooping switchback ramp over John Paul Jones Park. The pedestrian path on the southern side would be accessed via a stacked series of ramps closer to the water’s edge.

The complicated engineering contributes to the project’s cost estimates, which consultants put at between $300 million and $400 million. MTA board member Allen Cappelli told the Advance the cost was “very difficult to justify.” Council Member Debi Rose said it was “daunting,” and Assembly Member Nicole Malliotakis also said cost could be an obstacle.

The numbers may seem big compared to the estimates in DCP’s 1997 report, which said a new bike path could cost an inflation-adjusted $60 million. That plan proposed adding paths between the bridge’s suspender cables, which consultants told the Advance is not a realistic option.

Advocates are looking to work with the MTA on the project’s details, including modifying the design for ramps on either side of the bridge. “[The Harbor Ring] urges their engineers to also add a more robust range of possibilities,” said Harbor Ring committee member Dave ‘Paco’ Abraham. “These include potentially converting an existing vehicular lane as well as crafting more direct approaches to a pathway which could mimic the existing roadbed rather than building brand new ramps from the greenway below.”

Removing a lane of car traffic on the bridge might be less expensive, but could face challenges from traffic engineers and local politicians who otherwise support biking and walking access on the bridge.

One of the reasons the MTA decided to do the feasibility study now is because the agency will be taking on a major reconstruction of the lower level, which hasn’t been rebuilt since it opened in 1969. Replacing the existing structure with modern, lighter materials could make it feasible to add new paths on either side of the lower level. To accommodate the paths, consultants say the lower deck will have to shed approximately 12,000 tons of weight.

The upper deck is currently being reconstructed with newer, lighter materials and will accommodate a new high-occupancy vehicle and bus lane, slated to open in 2017.

“Though pathways’ implementation is already long overdue, such serious deliberation has never before been put into this already widely popular concept,” Abraham said. “While all details to better connect the boroughs are extremely preliminary, it is most certainly in the city’s best interests to ensure valuable public resources bring the structure into the 21st Century.”

The rally begins at noon tomorrow on Shore Parkway at the end of Fourth Avenue in Bay Ridge. The final feasibility report, part of the Verrazano-Narrows Bridge Master Plan, is expected sometime next year.