UPS drivers try to avoid left turns because their research has shown that it’s actually more efficient to simply do as many rights turns as possible. When you do a left turn you have to wait for people as well as oncoming traffic, even though you have the green light. With a right turn, generally speaking, the wait is not as long. If you can avoid a dozen or so left turns that time adds up. You would be better off turning right, delivering your packages down that street, and then making a series of rights and moving along.