Police have to search and seize your documentation in order to successfully execute a traffic stop. Isn't this a violation of the 4th Amendment?
The fourth amendment does apply to traffic stops.
In general, they are a violation of the fourth amendment in the absence of reasonable suspicion or probable cause. Even then, there are some circumstances in which suspicionless stops are acceptable to the Supreme Court, most notably in roadblock-style checkpoints for enforcing sobriety or immigration. See, for example:
- Michigan Department of State Police v. Sitz (on Wikipedia)
- United States v. Martinez-Fuerte (on Wikipedia)
Most traffic stops, however, occur after an officer observes a traffic violation. This gives the officer the necessary justification to detain the motorist. Wikipedia says:
A brief, non-custodial traffic stop is considered a "seizure" for the purposes of the 4th Amendment and must therefore be supported by reasonable suspicion or probable cause.
In constitutional law in the United States, a traffic stop is considered to be a subset of the Terry stop; the standard set by the United States Supreme Court in Terry v. Ohio regarding temporary detentions requires only reasonable suspicion that a crime has occurred or is about to occur.
You can also read more about Terry v. Ohio on Wikipedia.
You may disagree with the Supreme Court on the question of whether suspicionless sobriety or immigration checkpoints should be allowed under the fourth amendment, but the way the system works, such stops are allowed under the fourth amendment simply because the Supreme Court has said so.