That's what he see (or doesn't see) in his mirrors. Point being it's easy to lose a car in the blind spot on the highway. I see people doing that all the time to trucks, jump quick into the lane next to the truck while in the blind spot.
The trucks aren't dangerous its the cars around them that zoom in and out of traffic and go flying in and slam on the breaks and are just stupid in general. If you look at statistics the truck isn't usually at fault and when it is its either drugs to stay awake because they are over worked or they fell asleep at the wheel. In the us tractor trailers are only allowed to be on the road for 8 hour at a time but you wont keep your job that way so 2 sets of log books drivers know it company knows it and cops know it but very little being done to stop it. a few companies doing gps to put a stop to it but I have my doubts about there success rate and honesty.
The front of the truck blocks him from seeing
Also again, he is looking forward