Punto de Patrulla Fronterizo

As in US Border Patrol checkpoint. 
Most people might think that the Border Patrol patrols the border.  This permanent BP checkpoint is about 40 km/25 mi north of the Mexican border on Interstate 19 (25 km south of me).  There's no stopping required when you're driving south but there are a slew of cameras pointed in your direction.  You can see some of them on the left side of the photo. They are solar powered.  (Notice the radar tower on the right, too.)

The presence of Border Patrol vehicles and helicopters are a fact of life in southern Arizona but most of us, especially small tourist towns south of the checkpoint, aren't fond of having to pass through a checkpoint within our own borders.