If you have been waiting for your package and notice the UPS driver finally pulls up to your house, you may be surprised to see that the UPS van does not have any doors––or at least it looks that way. However, UPS trucks have sliding doors that retract into the side of the truck instead of “car-like” doors that open outwards. This is because sliding doors can better avoid obstructions when opening, such as other cars, mailboxes, or tight alleyway walls.