At what pressure should the low pressure signal activate in the air tank?

The correct answer is that the low pressure signal should activate when the pressure drops below 60 psi. This threshold is critical for ensuring the safety and functionality of the air brake system in commercial vehicles. Air brake systems rely on compressed air to function effectively, and a drop in pressure can indicate a potential problem, such as a leak or failure in the system.

Activating the low pressure signal at this level helps alert the driver to address the issue before it becomes critical, ensuring that the vehicle remains safe to operate. Maintaining adequate air pressure is essential for the effective performance of both the service and emergency brakes. Allowing the pressure to drop too low can lead to brake failure, which poses significant risks while driving.

The other options of 50 psi, 70 psi, and 80 psi do not align with the standard regulations and safety guidelines for low pressure warning systems, which ensures that drivers are adequately warned before reaching a potentially unsafe operating condition.