Generally, a traffic stop is considered reasonable—and therefore legal—if police: 1) have a legitimate reason (called “reasonable suspicion”) for stopping the motorist in the first place, and 2) conduct the roadside detention in a reasonable manner.  Officers cannot randomly engage in roving stops of drivers to check licenses and registrations.

In 1990, the United States Supreme Court ruled in Michigan Department of State Police v. Sitz, 496 U.S. 444 (1990), that sobriety checkpoints, also called DUI roadblocks, are permitted. The Florida Supreme Court established standards for this procedure in State v. Jones, 483 So. 2d 433 (Fla. 1986).  Law enforcement officials must conduct sobriety checkpoints so as to minimize the discretion of field officers. Written guidelines should cover in detail the procedures that field officers are to follow at the roadblock, and police should provide both proper lighting and sufficient warning on the roadway in advance of the stop.