Sobriety checkpoint

A random checkpoint is a military and police tactic. In a military context, checkpoints involve the setup of a hasty roadblock by mobile truck- or armored vehicle-mounted infantry to disrupt unauthorized or unwanted movement or military activity and to check for valid identification and search for contraband, fugitives, or weapons that are not permitted in civilian hands. Random checkpoints are set up to achieve surprise, as opposed to known permanently located checkpoints, which suspects could circumvent. They are often established in locations where they cannot be observed by approaching traffic until it is too late to withdraw and escape without being observed.

Patrol car-equipped police units regularly use random checkpoints to detect drivers who are suspected of impaired driving. Police also use hastily set up roadblocks to check cars and car trunks when they are pursuing an armed and dangerous fugitive. As with military checkpoints, sobriety checkpoints and fugitive roadblock searches are located in an area where drivers cannot see the checkpoint until it is too late to withdraw, and checkpoints are only set up on a temporary basis.

The unit establishing a military checkpoint must carry or obtain the materials necessary to construct it. It might use a large vehicle, or multiple vehicles, such as armored personnel carriers to block the road. In addition to blocking the road with vehicles, the road may also be partially blocked with concertina wire or heavy objects, such as sandbags or concrete blocks. The vehicles might be positioned to partially or entirely block the road or route. The search area might be the space between multiple vehicles. might be positioned at each end of the checkpoint and are covered by mounted or dismounted machine gun positions. A reaction force may be designated and concealed nearby.

...
Wikipedia