In my days of being trained as cabin crew, we watched many videos and discussed many different accidents as case studies. We learnt that passengers really do behave like headless chickens in an emergency.
Most passengers will evacuate an aircraft from the door from which they boarded the aircraft. This may well be the longest way out, even though there is a door behind them. This causes pax to escape against the flow causing confusion between the pax that are going the "right" way. This all ends up in a complete farse with people running everywhere with no orderly flow.
The best form of speeding up an evacuation is education of the pax. This means more thorough briefings given to an attentive pax audience. This would be seen as scare moungering by the pax and would never be taken up.
I remember the seating plan for the B737 Manchester fire, and it is amazing to see who escaped from which seat out of which door. There was just no logic in it at all. Even seats two rows from a door went the other way. Utterly amazing and frightning.