In subway cars equipped with lead storage batteries, for which purpose are these batteries least likely to be used?

Lead storage batteries in subway cars primarily serve to provide power for various auxiliary functions such as lighting, operating door systems, and supporting safety systems. While these batteries can supply power to the train's electrical systems, traction motors, which are responsible for propelling the subway car, typically rely on a different and more robust power source.

The main reason the batteries are least likely to be used for supplying power to traction motors is that traction motors require a significant amount of electrical power to function effectively, especially for acceleration and maintaining speed. This power is usually generated by larger propulsion systems, such as overhead lines or third rail systems, which are specifically designed to deliver the high current necessary for traction purposes. Lead batteries, due to their limited capacity and output, are not suited for this demanding requirement. Therefore, it's more accurate to say that while they can technically be involved in some aspects of traction, their primary roles do not include supplying power directly to traction motors.