Is there a different standard for state or federal roads? My understanding had been that reasonable suspicion was needed to search the driver's person as well as any areas of the vehicle immediate accessible to the driver or passengers, but that a locked compartment (glovebox, trunk, suitcase, etc.) which was not readily accessible required probable cause unless some other exception to the warrant requirement applied.
I'll admit I'm rusty in this area of the law, so I won't take it personal by any means if I'm due for a correction.
It's called a Terry Search after the name of the Supreme Court decision that an officer may search the passenger compartment for weapons for officer safety, without probable cause. A locked glove box is still part of the passenger compartment.