What must a driver carry when operating a commercial motor vehicle outside city limits during specific hours?

When operating a commercial motor vehicle outside city limits during specific hours, the requirement to carry three flares, three red electric lanterns, or three red portable emergency deflectors is crucial for safety. These items serve as essential equipment for signaling during a roadside emergency or breakdown, especially in low visibility conditions or at night.

Having these emergency signaling devices accessible and properly maintained is vital for alerting other drivers of your presence and potential hazards, thereby reducing the risk of accidents. The requirement is designed to enhance safety not just for the driver but also for other motorists who may encounter the vehicle. These tools are part of the regulations established to ensure that commercial drivers are prepared for emergencies, promoting safety across highways and roads.

The other options, while beneficial in their own right, do not specifically address the requirement for visibility and signaling during commercial vehicle operation in the defined conditions. An emergency fuel can, a first aid kit, and a spare tire all play roles in vehicle maintenance and emergency preparedness, but they do not serve the immediate purpose of alerting other traffic in the event of a roadside emergency.