What is the importance of checking the bus's air conditioning and heating systems during a passenger vehicle pre-trip?

HVAC is a passenger safety system, not just a comfort feature: HEAT: In cold climates, a heating system failure can endanger elderly passengers, children, and those with circulatory conditions; DEFROST: The defrost system is a VISIBILITY safety system — without it, windows fog or ice over, impairing the driver's view; AIR CONDITIONING: In summer heat, particularly for charter and intercity buses, AC failure in a sealed vehicle can cause heat illness and medical emergencies among vulnerable passengers; REPORTING: Any HVAC deficiency must be noted on the DVIR; a bus operating in extreme temperatures without functional HVAC may need to be held until repaired.