As of today, you should go ahead and disregard any nonsense the pizza guy gives you about a "delivery radius". Because after one daring Pizza Hut employee's quest to deliver a 'za to a customer on a moving train, it's pretty clear a limit does not exist.
Reddit user photosoflife posted an inspiring set of pictures yesterday chronicling the delivery challenge she offered Pizza Hut: bring me a pizza in the middle of my four-hour train ride. After telling the Hut where her next stop was (the Newport Station in South Wales), she gave the conductor a heads up and waited to see if her pizza would actually arrive. SPOILER ALERT: It totally did.