This is a great question and it's really interesting because your job isn't a typical office job. So not having a lot of face-to-face interaction with your job puts a wrinkle in the whole thing.
I've written about http://www.thewriterscoin.com/category/better-employee-series/ to work your way up and get a pay raise, and I think some of the ideas still apply to you.
I would say that your best bet is to keep doing the good work you're doing and then come up with something new. A plan, an idea, a system. Something that will make your job or the way your company does business more efficient. That might save them money. That might make other drivers happier/more productive.
If you come up with some idea that shows your thinking bigger than just your route, it'll show that you a) care about the bigger picture of the company, and b) you're a self starter.
This, along with the good stuff he's already heard about you, could help your situation.
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