According to this article, UPS drivers do not take left turns (well, rarely make them. Left turns take up less than 10% of UPS drivers turns. This policy of no left turns was put into place back in 2004 and has saved the company over 10 million gallons of fuel. It has also reduced traveling time and carbon emission from the trucks.
The company used math in order to come up with this new routing tactic. It seems to be paying off. This article talked about how if all people agreed to do this then it would create many benefits for the environment, traveling, and safety (less crashes).
I personally do not think people would ever agree to it, but it is extremely interesting. It is awesome to see companies making changes that help environmental issues!