https://theconversation.com/why-ups-drivers-dont-turn-left-and-you-probably-shouldnt-either-71432

UPS have designed their vehicle routing software to eliminate as many left-hand turns as possible (in countries with right-hand traffic). Typically, only 10% of the turns are left turns. As a result, the company claims it uses 10m gallons less fuel, emits 20,000 tonnes less carbon dioxide and delivers 350,000 more packages every year. The efficiency of planning routes with its navigation software this way has even helped the firm cut the number of trucks it uses by 1,100, bringing down the company’s total distance travelled by 28.5m miles – despite the longer routes.