According to state policy, how often should air tanks be drained?

Draining the air tanks whenever the bus is parked and left unattended is crucial for maintaining the air brake system and preventing potential corrosion or freezing issues within the tanks. Air tanks can collect moisture from the compressed air, which can lead to rust and damage over time if not properly managed. By ensuring that the tanks are drained regularly, particularly when the bus is not in use, drivers and maintenance personnel can prevent the accumulation of water and other contaminants. This practice helps keep the braking system operating efficiently and extends the lifespan of the equipment.

The other options, while they may address specific issues, do not encompass the proactive approach required for regular maintenance of air tanks. For instance, relying on an alcohol level or temperature conditions fails to address consistent preventative maintenance, which is essential in ensuring safe and reliable operation of the bus. The recommendation from the maintenance department, although important, does not provide the regularity and assurance needed from the driver's perspective. Thus, the best practice is to ensure the air tanks are drained when the bus is left unattended.