Simulate the scenario with water in a pool with a tiny pipe opening at the bottom if the pool leading down. The water will shoot out with a high velocity this means the pressure in the pipe will be higher than pressure in the pool. If you apply this analogy to people and exits, it means that the people directly in the exit hallway( the pipe ) will experience a high change in speed, and since people aren't fluid, friction, thus making their escape more difficult.
The pressure in the pipe is the same as the pressure in the pool. Additionally, the meter^3/minute is the same in the pool in the pipe, but the with the pipe, the meter^2 is much smaller. So, to keep the same rate of fluid, the meter/minute (speed) has to be much higher.
