I thought that the conventional wisdom was that one does not simply walk into it. 
The guy who said that was shown to be incorrect in later scenes in the documentary.
My cousin, two cars back from a stop light had someone walk into her car and flip her off. The walker was on her cell phone of course.
This was a college campus. We are doomed.
A woman was killed when she decided to open the trailer (think Airstream) at freeway speeds. It was a suicide door in that the air shoved the door open fully from a crack immediately and the woman holding on to the door couldn’t let go in time and was thus thrust out into traffic … at freeway speeds.
I can see how this was a bit different but opening a door at freeway speeds is the real issue here. It’s a special kind of stupid. I’m not sure engineering can fix that.
I’m pretty sure carrying a passenger in a trailer under tow is illegal to begin with. Because they’re not crashworthy at all. And the hitch arrangements are far from foolproof. It would suck mightily to be in a trailer that came detached from its tow vehicle at speed.
Perhaps there’s an exception for so-called 5th-wheel trailers, but I’m not arsed to check.
But yeah, overall we’re dealing with multiple counts of special kind of stupid.
Cite:
So not universal, but in a majority of states it’s illegal, with some wiggle room depending on the type of trailer. Yes, 5th wheel options are more permissive but with other caveats as well. So yeah, special kind of stupid, and frequently the illegal kind of stupid.
The trailer story underpins the reason I was always told they were called suicide doors. If they become unlatched, the air pressure will open them whereas with standard doors, if they open in flight, the air pressure will tend to close them.
My old truck had doors like that. I didn’t often have people in the back seat, but it definitely made putting stuff in the back seat easier, it gave you a nice wide opening.