All you’ve got to do is look at the companies working on it. Uber. Amazon. Big trucking companies. There’s a market. There’s a big market.
There's a market for overpriced status goods. They have to work right basically 100% of the time, or the market doesn't ever appear. Segway works, unless the passenger is a bit too heavy, or (in the case of a good sized chunk of the US population) experiences actual weather, like sudden downpours, ice storms, icy roads...
There's a market for cargo / parcel delivery by drone, but unless it runs someone down or falls out of the sky onto someone's head, no one cares if the package gets destroyed, there's more where that came from.
I could see the semis running as bots or remote control over the vast stretches of nowhere and a driver getting behind the wheel when getting close to civilization.