My suggestion is making the private car also be locked when the owner is offline unless the owner himself didn't lock his car.Only the cars owned by State are free for every citizen to use.If one wants to drive a car that has been locked,he should do it in a criminal way with a tool named lockpicks which can be bought from tool stores.To force a vehicle door open,he needs to walk close to the vehicle and enter /picklock.Meanwhile there will be a message saying that <player's name> picks the lock of a <vehicle's name>.The process of a car thief picking a lock is certainly supposed to take some time.During the process he can stop this act anytime he wants.Once the car lock is broken,it will remain unlocked until it respawns.All these only work on the vehicles that are not restricted to specific duty.If a police finds a person picking car lock,he needs to suspect the person for stealing vehicle.And if the driver is confirmed not to be the owner,police should also investigate into it.Picklocks as an illegal item to be utilized,players can determine whether carrying it or not like explosives and also it will be lost after each death.