Why would we assume that the advent of driverless trucks would be bad for trucking support jobs? Those folks are doing stuff like maintenance or loading that still has to be done. Moreover, other jobs will be created, in designing and maintaining the new systems. Someone has to map all those roads.
But I think it will be a while before we get to a fully autonomous vehicle with no people in it. The “driverless truck” that Santens links is not actually driverless; it’s partially autonomous. If it foresees something it can’t deal with, such as heavy snow, it signals to the driver to take over; if the driver doesn’t respond, it slows to a stop. That’s an improvement in the lives of truck drivers, not a job killer.
Of course, this is only the beginning. The technology will get better and better. I do expect that eventually, our roads will be autonomous. But I’m not as optimistic as I used to be, because it turns out that Google’s achievement, while amazing, is not quite as amazing as many people seem to think.