What "better jobs" are you thinking of that a typical truck driver could be realistically trained for? It reminds me of when the US steel mills closed in the 1970s and 1980s and people said -- "we can just retrain these workers for a lucrative computer career!". Didn't really happen. The elimination of unskilled/low-skilled labor through automation is major problem for society that is only going to get worse.
One of the big challenges we face as a society is managing these kinds of transitions. In 1900, the majority of Americans worked on farms. We managed that transition, but we had decades to do so. If self-driving cars eliminate all driving jobs in a single decade, the dislocation will be immense.
This is where government action will be required; this is a society-wide problem that needs a society-wide solution.
In my experience, many people (I don't like the word 'middlings' for some reason) think job to job instead of about a career. And then they have job problems.
Likewise, many people think paycheck to paycheck instead about longer-term finances. And then they have cash flow problems.
Isn't part of the solution to get employers and employees to talk to each other in terms of career trajectory, professional development, and skills marketability?
Couldn't part of the power imbalance be solved by getting employers to think again about giving out dead end jobs in dying industries? Right now we put the onus on the employee to recognize the problem and demand a better deal. Assuming automated freight trucks become a thing, shouldn't trucking companies say, "Hey, work for us. We'll have you trained for better jobs by the time the truck drives itself!"?