The United States Supreme Court has held that a search incident to a valid arrest for a traffic violation is not limited to a frisk of the arrestee's outer clothing; the custodial arrest itself gives rise to the authority for a full search, regardless of whether there exists either further evidence of the crime or a belief by the arresting officer that the arrestee is armed or dangerous.
United States v. Robinson, 414 U.S. 218 (1973).
William L. Steiner,
Criminal Law - Fourth Amendment - Search and Seizure - Scope of Search,
Duq. L. Rev.
Available at: https://dsc.duq.edu/dlr/vol13/iss1/19