No Roadblocks on Interstate Highways
The federal government will not allow roadblocks on interstate highways for a variety of reasons, starting with safety concerns. Hence, getting to the interstate for purposes of avoiding a roadblock is one basic strategy to avoid a roadblock. However, the police know that most traffic will seek access to an interstate to travel home. Hence, the police will try to set up their sobriety checkpoints along one of these "feeder" roadways. Knowing or guessing which roadway has the roadblock set up is the gamble. The teams of sobriety checkpoint officers decide when and where they will establish the checkpoint and then converge at an appointed hour to block traffic on that street. Having the ability to allow cars to pull over to the shoulder or adjacent parking lots is a key safety concern of police at these roadblocks.
Virtually every roadblock has a "chase" car. This is an officer waiting in an idling vehicle at a strategic vantage point to see any vehicles that attempt to avoid the roadblock. These "chase" officers assume that ANY vehicle turning away from the roadblock is trying to avoid detection for possible impaired driving. Several cases across the USA have held that citizens who do not wish to be delayed at a roadblock, or citizens who believe they have happened upon an accident scene that is delaying traffic may find a safe, legal way to leave and not pass through the safety or sobriety checkpoint. However, if you make an abrupt, unsafe or illegal maneuver in turning around, this will usually justify the chase car pulling you over.
Common Strategy for Roadblock Location
Officers will usually position the roadblock location around a bend in a road, or over the crest of a hill, so that cars approaching the location will not have any side street to use to avoid passing through the checkpoint. Safety issues can pose a problem for the police if visibility of oncoming cars is limited or restricted by such hidden but dangerous locations.