Nope. They just kept going around the island following the roads

Vehicles can be made to drive themselves Description: If you are driving a vehicle and exit it while moving (i.e. don’t stop before leaving it), it will continue to drive at the same speed you left it at, auto-piloting itself around the island. It’s not entirely clear why this is the case, but it’s possible the vehicles are the same type of “entity” as the NPCs roaming around and that vehicle speed isn’t automatically cleared when you leave it, causing it to roam around too at the speed you inadvertently set for it. If this is true, there are interesting implications for potentially driving and/or setting the speed of NPCs. Interestingly, the vehicles don’t seem to move indefinitely (they don’t slow down, but will eventually stop moving) so perhaps some background system on the island periodically tries to ensure vehicle movement is set to 0.