A flivver was kept aboard a starship and used for emergency transport. It could support a handful of humanoids and had an exterior hatch for boarding. Its engines were powered by a type of portable fuel.
In 2267, the USS Enterprise came upon a disabled flivver. Spock donned a spacesuit and boarded the vessel through its hatch. He rescued Allura, an unconscious female human. The distress was a ruse so that she could get aboard the Enterprise, but Spock uncovered the deception when he attempted to refuel the ship and found it fully fueled. (TOS comic: "The Hijacked Planet")