The allowable maximum outage time of the passenger walkway emergency lighting is 45 seconds - that is, from the moment of the loss of illumination which was provided by means of the normal power supply, to the time when full specified illumination is provided. This requirement eliminates the use of arc-type lamps as an emergency light source. Normally, quartz-halogen incandescent lamps would be used, but on a separate emergency circuit to save lamp life.