I think "created an algorithm" is probably overselling it a bit. Clearly they already had a route planner, didn't they just modify it to add extra cost to a left turn?
Two papers on the subject, applying turn costs to the two most popular speed-up techniques (I don't know if UPS uses either of these, though):
https://algo2.iti.kit.edu/download/turn_ch.pdf
http://i11www.iti.uni-karlsruhe.de/extra/publications/dgpw-c...
The first author of the first paper now works at Google, and the authors of the second paper used to work at Microsoft Research and now are at Apple and Amazon. Make of that what you will :)