As the Department of Transportation sees it, installing bicycle lanes on 9th Street in Park Slope will improve safety for pedestrians, motorists and cyclists alike.But some are opposed to the plan, rejecting the agency's safety claim and arguing instead that the lanes could forever alter life along the roadway.The bike lanes will effectively "stop us from using our street," Robert Levine, co-president of the 9th Street Block Association, told Community Board 6's Transportation Committee last week.Levine, a member of the board, said the lanes would make it harder for residents to double-park in order to drop off packages at home, or pick up family members.Obstructing a bicycle lane carries a fine of $115.Double-parking in an area with a scarcity of spots is simply "realistic," Levine said. "That's life in the city," he said.DOT officials came before the committee to detail the plan, which could be implemented in July.Ninth Street, as currently configured, holds excess capacity, leading to higher motorist speeds, according to Joshua Benson, the director of the Department of Transportation's Bicycle Program.The plan calls for 9th Street's four lanes to be pared down to three."Having the extra lanes [on 9th Street] really allows people to speed," Benson said.If previous projects are any indicator, the street will be made safer, he said.Benson said cutting lanes on Gerristen Avenue and Vanderbilt Avenue has proven to reduce motorist speeds.He noted that 9th Street carries some 11,500 cars daily, while Atlantic Avenue carries 26,000. Both roadways have the same design.As the plan stands, the bike lanes, one in each direction from Prospect Park West to Court Street, would not be physically separated from the roadway.One moving lane in each direction will be removed and replaced with a left turn lane in the center, Benson said."We really wanted to make the street safer and more comfortable for all users," he said.The project will cost approximately $62,100, according to the DOT.As the lanes will not be physically separated from the roadway, implementation will be fast, as all that is needed is for markings to be painted on the street, and signs to be installed.Benson said the lanes will connect cyclists to many "of the great destinations in Brooklyn."The 9th Street lanes will meet up with planned bicycle lanes in Red Hook and act as an extension to the Brooklyn Waterfront Greenway."I think we have a really exciting plan," Benson said.Levine said a bike lane already exists on 3rd Street, and that lanes on 9th Street, the busiest street in the neighborhood, would imperil bikers, and that pedestrian safety would also be negatively affected."Bike traffic is harder to see from the curb than vehicular traffic, and given the large number of people crossing the street at mid-block