Staged? Yes and no, certainly all are not staged. Not all the wrecks are on that road. They are wrecks from different highways , creative editing and over an extended period of time. Some of the fake empty road "sliding tow truck" on empty roads with no cars around scenes are most certainly staged as well as the personal drama being staged.
I stopped watching after a very dramatic incident. The only problem when they hooked up and towed away the highway was empty at around 8pm in the evening, there should have been traffic backed up for miles in both directions. SO staged. I then began to notice so many empty roads during towing jobs or how traffic disappears. Things changed lanes, roads changed and even time of day changes. I've also see where the put in stock footage of traffic. One line of trucks appeared in a couple episodes lined up in the same order.
One of the more ridiculous staging was when a tractor trailer went over an embankment. They pulled the empty trailer out that was supposed to have a load in it, then they had to get the road open to traffic. But when they panned the camera the road was empty for miles. Then when they pulled out the tractor portion, magically the whole undercarriage, engine and drive train was gone. They winched up a clearly salvaged cab in very dramatic fashion. Strangely the drive train was not there nor was it winched out.