I agree and disagree with both these posts.

I've worked at A LOT of trucking companies and very few have ever ran fixed routes. Two of the larger companies I was with had about 1/3 of their trucks on round-trip or dedicated freight but that meant planners needed to reach out to brokers or try to match up scarce customer freight out to the rest of the trucks. As of right now, since the market is so soft long-haul OTR is actually just as cheap as rail. Now, of course, that is subject to change but in the current market I have actually ceased rail quotes due to the fact that my customers would rather ship it just as cheap on a truck when it can get there quicker than rail. (Except for LTL of course)

Dedicated customer freight can also be brokered out and not put onto trucks and it's not always the same trucks taking this freight. Other times it is... some freight is one-way and some is round-trip. I've seen a lot of one-way trip drivers get messed up because they cannot find a load out of the market they are currently in.

That being said, self-driving trucks would cut-down the transit times because breaks will no longer be needed for drivers. There's a lot more variables to account for though such as affordability, functionality, etc. However, you won't see everyone switching over to self-driving trucks right away especially if they are costly.