Is there a legal limit to people in a truck?

Might have been some kind of school. When I was in school we'd have five people in the truck.

 

I'd guess it'd be like a car, however many seat belts there are.

 

It depends on the company. CR England will stuff as may in as they can stack beds.

 

As the economy tanks, you're going to see alot of that. It was happening back in 09 and 10. Whole families living in a truck ... mom and dad driving and 2 or 3 kids or multiple couples.

 

The truck we students drove while at the Swift Academy had the bunks removed and 3 additional chairs, with seat belts, where the bunks were before. Once we started driving on the road, we had 4 students and the instructor. We'd each drive about 30 minutes to an hour and then swap students. We'd stay out all day, so we drove multiple times each day. So, it wasn't bad like it might sound. At that point our class was a total of 8 students. We got along really well and were a pretty tight bunch. So, it was all good.
But, the situation described by the OP sounds absurd. I can see 3 in a truck, because you can use the straps thingy on the bottom bunk, but for more folks, can't see how it would be legal for safety concerns with not enough restraint/seat belts to be legal and safe.

 

I counted 9 in this pic. Probably at least 15 more in there. Pick only short skinny ones and the numbers go up LOL

 

That's right, saw that often back then. I remember a woman and 4 guys climbing out of a truck, at the fuel islands at a truck stop in AR. They were all clean and wearing decent clothes. They fueled the truck and went back to the interstate.
Very common to see whole families living in a truck.