While the need to make routine checkpoint stops is great, the consequent intrusion on Fourth Amendment interests is quite limited. The stop does intrude to a limited extent on motorists' right to “free passage withoutinterruption,” Carroll v. United States, 267 U.S. 132, 154, 45 S.Ct. 280, 285, 69 L.Ed. 543 (1925), and arguably on their right to personal security. But it involves only a brief detention of travelers during which
“ ‘(a)ll that is required of the vehicle's occupants is a response to a brief question or two and possibly the production of a document evidencing a right to be in the United States.’ ” United States v. Brignoni-Ponce, supra, 422 U.S., at 880, 95 S.Ct., at 2579.
Neither the vehicle nor its occupants are searched, and visual inspection of the vehicle is limited to what can be seen without a search. This objective intrusion the stop itself, the questioning, and the visual inspection also existed in roving-patrol stops. But we view checkpoint stops in a different light because the subjective intrusion the generating of concern or even fright on the part of lawful travelers is appreciably less in the case of a checkpoint stop.