[brc]

It would seem to me that the visual obstruction of the column causes as much as the physical obstruction. An interesting twist on the experiement would be to construct a clear obstruction that people could see through - and see if that impeded the flow because of impatience at being nearly outside.

Also I wonder if a fake wall with 5 exit doors in it (close to each other), that obscured the one actual exist would speed up flow - presuming people selecting the general area of the exit first, then the detail of the exit point second. If there were 5 single doors it would separate the flow to the actual choke point, but without producing the same type of barricade.

If this research turned out to be widely applicable, I wonder if placing airline staff in front of a door would speed the exit of people through it?

I also suspect there is an optimum shape for the obstruction, and I expect that it isn't round.

All interesting stuff.