What is it called when a police officer slows on the freeway and drives across all lanes of traffic?

This maneuver by a police officer is typically known as a "rolling roadblock." It is often used in situations where there is a need to slow or bring traffic to a complete stop, such as during a high-speed chase, a hazardous materials spill, or a major accident. The police officer will slow down and position their vehicle diagonally across multiple lanes of traffic, with the intention of gradually slowing down any vehicles following them. In some cases, officers may be positioned at exit ramps to divert traffic away from the blocked area. The use of a rolling roadblock is considered a safe and effective way to control traffic flow in potentially dangerous situations.