The amazing thing here is that rats are intelligent enough to learn to drive, albeit a simple vehicle. That alone is newsworthy, without the experiment on stress reduction.
Ehh, it's not clear to me that humans should be particularly good a driving. It's not like we evolved for it, we can just understand spoken instructions. I'm not convinced that an octopus, a dolphin, a raven, or a cheetah would necessarily be worse at the task than a human (given training in the proper format) -- it's perfectly concievable to me that a cheetah might have evolved to handle object avoidance at higher speeds than humans have, for example.