In Maryland v. Wilson, the United States Supreme Court held that a police officer may order a passenger of a lawfully stepped car to exit the vehicle. This "bright-line rule" allows these intrusions as a matter of course and does not require case-by-case determination.
"Maryland v. Wilson: The Fading Fourth Amendment,"
Mercer Law Review: Vol. 49
, Article 12.
Available at: https://digitalcommons.law.mercer.edu/jour_mlr/vol49/iss3/12