A police officer was rushed to the hospital this morning after a collision on the Brooklyn-Queens Expressway (BQE) that sent his car flying off the roadway and onto the street below. Police say the off-duty officer was going eastbound on the BQE when another car suddenly slammed into him from behind, causing his vehicle to crash through the rail, hit a retaining wall and plummet down to Meeker Avenue. The bumper from the officer's Nissan Sentra landed more than 30 feet away from the rest of his car.Both the officer and the driver of the other car were taken to the hospital, where they are listed in stable condition. Truck drivers who were at the scene say accidents such as this one happen all too often on the BQE, and motorists must be more cautious.