Konkordski wrote...
I can't see that anyone would seriously believe that narrowing the seat pitch would help anyone.
Well, I don't know any of the specifics regarding the recent Cranfield study but as I wrote earlier - it doesn't seem entirely impossible that smaller seat pitches could speed evacuation.
If there is a finite rate at which people can move down the aisles and out of the exits before they start to pile on top of each other and cause blockages then restricting flow into the aisles could conceivably help.
It all depends on which part of the exit route is the rate limiting step. It seems very likely that if there is a maximum rate at which people can pile out of an exit - if there are in fact no limits on how fast people can get to and congregate at the exits then blockages could easily develop.
Imagine a cabin with no seats at all, and then think what would happen during an evacuation - everyone would rush to and crowd around the exit doors most likely slowing the rate at which people actually leave. A bit like what's going on at the door on the left here...
Or as illustrated in the figure on the top left here...
So in a normal cabin - the manner in which the aisles limit the flow towards the exits may, perhaps counter-intuitively, actually speed the evacuation rate.
Now, as I said I don't know the details of the Cranfield study but I don't think we should be dismissing it out of hand. Of course any small benefits in terms of evacuation rate would need to be weighed against the other risks associated with cramped seating.
Also it is important to bear in mind that while narrower seat pitches may speed the evacuation rate slightly -
if they are used to pack in more people then they will also increase the number of people who need to be evacuated. Consequently, the net effect on the ability of a cabin to meet the 90 second rule may be zero. Unless of course, you narrow the seat pitch without increasing the number of seats - perhaps leaving large empty spaces for stretching and other activities (putting practice? Twister? dancing?)