...the last time we saw a pop-up driving down an Interstate with the roof up, it was I25 north of Denver. Incredibly, an Outfitter camper, blasting along the interstate WITH ROOF FULLY DEPLOYED traveling in the opposite direction. We can only assume that the rig was traveling at 65 to 75 MPH. Everything looked none the worse for wear (ie. perfectly stable).
Glad no one was hurt. Thinking about the myriad possible disastrous outcomes makes me think twice to ever want to venture out onto the Intertate highways following cargo-laden vehicles.
It also makes you wonder and consider how secure the roof clamp-downs are. I check ours before every outing, and replace the stainless screws into the camper sidewall aluminum framing with marine adhesive at ~4 year intervals. And check the roof-fascia integrity constantly.