Answer :
Final answer:
In a dual air brake system, the low air warning device must activate by 60 psi.
Explanation:
In a dual air brake system, the low air warning device is supposed to activate when the system's air pressure falls to a certain level. This is an important safety precaution in the operation of heavy-duty vehicles that use dual air brake systems. According to federal regulations, the low air warning device should activate before the air pressure in the tanks falls below 60 psi. So the correct answer to your question is 'C. By 60 psi.'
For instance, if dual air system, low air warning device, and 60 psi can be related to a tire gauge reading scenario. If we have a reading of 34 psi, and we add the atmospheric pressure of 14.7 psi, we get an absolute pressure of 48.7 psi which is still below the 60 psi safety threshold. Therefore, the warning device of the 'dual air system' would have already been activated.
Learn more about dual air system here:
https://brainly.com/question/32181708
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