What must a driver ensure regarding emergency exit warning devices?

A driver must ensure that emergency exit warning devices are working properly if they are present because these devices are crucial for passenger safety in case of an emergency situation. Properly functioning exit warning devices alert passengers about possible exits and help ensure they can evacuate safely and efficiently if needed. If the devices are not functioning, passengers may not receive the necessary information to navigate an emergency, potentially leading to dangerous situations.

The other options do not emphasize the critical aspect of functioning safety equipment. While it might be true that a warning device is only needed if there is an emergency exit, this does not address the importance of ensuring its operational status. Suggesting that these devices should be used during every stop implies an unnecessary action if the situation does not call for it, while stating they can malfunction without consequence undermines the importance of their reliability in ensuring passenger safety. The emphasis on functionality directly relates to the overall safety protocol that must be maintained in passenger transportation.