1. To ensure the convenience of passengers on and off, the maximum opening degree is controlled in 65° ~ 70°; 2. There should be no position interference with other parts in the opening process; 3. When the door is closed, it should be locked and reliable, and it will not be opened by itself in the driving. 4. Door mechanism control anti-easy, including close the door freely, glass lifting light, etc. 5. Good sealing performance requirements; 6. With a large transmittance surface, to meet the requirements of lateral vision; 7. There should be enough strength and stiffness to ensure the reliable work of the door, reduce the vibration of part of the door, improve the safety of the vehicle side collision, and prevent the door from sinking; 8. Good door manufacturing