driving in the United States, called legal

(1)It’s legal to take off all the doors and run without a side mirror
(2)Sideview mirror required lead is also available
(3)The reason for each is different, but the biggest reason is to save gas by reducing the weight. About 32kg per front door is less than this, but about 100kg is reduced in weight based on four doors
(4)There’s a door like this, too