What should the air pressure on the duplex air pressure gauge read for an M-3 train with the master controller in the MAX brake position?

The correct range for the air pressure on the duplex air pressure gauge for an M-3 train with the master controller in the MAX brake position is indeed 130-150 PSI. This pressure range is vital for ensuring that the braking system operates effectively and safely.

When the master controller is set to MAX brake, the system requires a higher air pressure to ensure full braking capability. The range of 130-150 PSI indicates that the system has an adequate supply of air pressure, which is necessary to apply the brakes forcefully and quickly in emergency scenarios. Maintaining this specific pressure range is crucial for reliable train operation, particularly in terms of safety and braking efficiency.

Understanding this range is important for operators and maintenance personnel as it helps ensure the train's air brake system is functioning as intended, providing the necessary performance during braking events. The other options do not fall within the operational guidelines for the M-3 train and would indicate either insufficient performance or excessive pressure which could pose safety risks.