Just trying to be creative here:
if you define all people as being in wheelchairs with a certain velocity and group them so that they move together in groups according to cars (lets say 4 or 5 people group). that might give you a rough estimate of egress time (since you anyway need about 50% higher ASET than RSET, rough should be good enough).
you will have to see how you keep a certain distance between groups (simulating the distance between cars).
of course, visualization will not be cars...
