Police officers swerve on the freeway as a deliberate technique called a "traffic break" or "rolling roadblock." This involves cautiously swerving back and forth across multiple lanes to slow down or stop the flow of traffic behind them. The purpose is to alert drivers to reduce speed, prevent passing, and create a safe environment for clearing hazards like stalled vehicles, road debris, accident scenes, or other dangers ahead. This technique helps emergency responders manage traffic flow and ensures safety for everyone on the road. Police typically have their emergency lights on during this maneuver to signal an upcoming hazard or situation requiring traffic control.