The stretch of Broadway in Lower Manhattan known as the “canyon of heroes,” which has hosted 200 ticker-tape parades, may soon be closed to most vehicular traffic, under a new plan the city is quietly floating among local representatives and community groups.

With construction projects in Lower Manhattan expected to produce unprecedented levels of traffic congestion this summer, the Department of Transportation is studying how closing Broadway south of Ann Street to all vehicles except city buses and speeding bus traffic on Broadway below Houston Street could alleviate traffic problems.

Making Broadway accessible only by mass transit would for some time require a police presence of 30 traffic agents working two shifts a day to reroute traffic, according to city officials. The expensive plan would be implemented only if construction at the Fulton Street Transit Center results in large swaths of gridlock in the neighborhood, according to a spokeswoman for the transportation department, Kay Sarlin.

No end date has been set for the contingency plan that could shut down Broadway to all cars. The city is not now considering any other options for dealing with potentially record-high levels of traffic congestion in Lower Manhattan this summer, according to Ms. Sarlin.
Demolition of buildings on the east side of Broadway at the site of the future Fulton Street Transit Center began a few weeks ago. Transportation department officials said they expect congestion in Lower Manhattan to peak in July as construction and demolition kick into full gear.

The Fulton Street Transit Center, which is expected to employ six platforms to connect 12 subway lines with the PATH by 2009, is one of 59 residential, commercial, and transportation projects currently under construction within a one-square-mile radius below Canal Street, including the huge Freedom Tower project at ground zero.

The construction projects create congestion by taking up street space and squeezing the same number of cars into fewer lanes. “We will keep the community apprised well in advance of any potential changes,” Ms. Sarlin said, regarding closing Broadway to cars.

So far, the transportation department has brought its traffic-calming plan before the board of the Downtown Alliance, which manages Lower Manhattan’s Business Improvement District. One of its board members, Joseph Kopel, then raised the plan with Community Board 1, which represents the area. The district manager of Community Board 1, Noah Pfefferblit, stressed that nothing is definite yet and that he hoped closing Broadway would be a plan of last resort. “The plan would be put into effect only if the traffic congestion becomes drastic in the future,” Mr. Pfefferblit said.

Council Member Alan Gerson, who represents Lower Manhattan, said through a spokesman that because he had yet to meet with the transportation department to discuss the plan, he would not comment for this article.

“We want to do everything we can to encourage the use of mass transit in Lower Manhattan,” Ms. Sarlin said. “With all of the construction in the area, this is going to be the best way to travel.”

As it considers closing an important thruway to cars, the city is simultaneously attempting to speed up its buses along Broadway below Houston Street in order to encourage drivers to switch to mass transit.

Beginning April 1, the transportation department will be constructing five “bus bulbs,” which extend the sidewalk into the street and thereby cut down on the time buses waste pulling out of traffic to pick up passengers from the curb and then reentering the traffic flow. The city will also be adding a bus-only lane in the middle of Broadway. The improvements are scheduled to be complete by June 1.

The bus bulbs, which cost the city about $100,000 apiece and span about 120 feet, will be blooming along Broadway at Houston, Spring, Grand, White, and Franklin streets. “They will improve commute times, reduce gas emissions, and make our city function better,” the executive director of Transportation Alternatives, Paul Steely White, said.

While Broadway’s bus bulbs are being constructed specifically to reduce congestion associated with the construction of the Fulton Street Transit Center, Ms. Sarlin said there is currently no timeline for their removal.