The Navitron Autodrive system is a system in trucks so they can drive themselves.
Homer had decided to drive a truck to Atlanta, after the truck's original driver, Red Barclay, had died from beef poisoning, he and Bart needed to drive 2200 miles in 10 hours. Homer took an entire bottle of pep pills which he purchased from a small shop and then along with some sleeping pills to "balance it out". However, he eventually fell asleep at the wheel. The truck then proceeded to drive itself. It drove down a cliff and stopped itself at The Gassy Knoll.
Next morning when Homer woke up, he was so amazed that he told two truckers about it. They explained him that every truck has the Navitron Autodrive systems installed inside so they can drive themselves. The two truckers then threatened Homer to keep quiet.
Despite of his promise, Homer soon told some tourists about the scam. When other truckers learned it, they chased him and formed a blockade. Homer let the system drive, but it told him that the system can't do it and jumped out of the trucker. Homer eventually got past the blockade.
At the end, one of the truckers suggested to stop using the Autodrive system and go back to using their hands and wits. However, they all refused it and decided to smuggle Beanie Babies as their new scam instead.