Safety First is a gear perk that raises your general defense while you are in a vehicle. Driving and flying through FND checkpoints draws a lot of fire, and this keeps Dani alive longer.
Damage that reaches you inside a vehicle is reduced. That matters most on open vehicles and when you drive through gunfire.
Wear the Croco Driver Helmet or Soviet Coat. Gear perks are fixed to the piece of clothing that carries them, so you get this one by wearing that piece, not by unlocking it in a menu.
Tank Commander and Tank Buster also reward vehicle play, so they make a natural set for a driving build.