Abstract: A system for controlling the amount of fresh air being introduced into a people mover vehicle. A variable flow exchange is provided based on the number of passengers in the vehicle thus controlling the amount of positive ventilation in relation to the passenger load. The people mover vehicle is electrically powered and, after the people mover vehicle leaves a station, the electric motor current is monitored and the vehicle speed is monitored. The motor current during the time that the vehicle speed is between about two miles per hour and about five miles per hour is proportional to the passenger load and, therefore, the ventilation requirements can be determined, and the appropriate amount of positive ventilation supplied, based upon the electric motor current monitored when the vehicle velocity is within the aforementioned range.