Bicycles and cars are grudging partners on Manhattan's congested streets, dodging and sometimes cursing each other as they share the road. But soon they won't have to, at least for a few blocks.The city plans to experiment with a heavily buffered bike lane in one part of the Chelsea neighborhood, City Transportation Commissioner Janette Sadik-Khan said. Bicycles will be separated from auto traffic by both a strip of pavement and a lane of parked cars.The design, which has been tried in Europe, will be installed within the next month on Ninth Avenue between West 16th and West 23rd streets, Sadik-Khan said."It represents the kinds of innovative ideas that we can explore to make the streets more livable," she said.The project will condense cars from four lanes to three, but Sadik-Khan said traffic in the area was light enough that the change wouldn't be a problem.The city announced a $1 million bike safety ad campaign Tuesday, aiming to get drivers and cyclists to look out for each other. Sadik-Khan has said 300 cyclists were seriously injured last year, 94 percent of them due to inattention or failure to follow traffic signs.The city also is promoting bicycle riding through helmet giveaways and other means, and one cycling advocate said he thought the protected bike lane would prove a powerful incentive.Noah S. Budnick, the deputy director of Transportation Alternatives, said many would-be city cyclists "say the traffic is too scary.""If you provide protected space for riding bikes, New Yorkers are going to use it in droves," he said.