This question came to me through my Facebook page on June 15th:

I found your website on Google. I have a question that I couldn’t find an answer to. I know hazmat placards must be visible from all 4 directions (with a few exceptions). But my question is this…specifically…
I have a 1-ton truck with a headache rack. Can I mount the front placard on the top of the headache rack so that it is 100% visible from the front? I would have the other 3 in the normal places. I read where it has to be mounted on both sides, front, & rear. It would not be actually “mounted” on the front, but it would be clearly visible. If it is acceptable, can you please tell me where it says it so that I can keep proof in the truck? Thank you for your time.

I replied the next day (6.16.16) and didn’t pretend to understand everything she was talking about:

Thank you for your question. I will reply later today or tomorrow.

Question: What is a headache rack?

The customer helped me out:

It is a metal guard that goes across the back of the truck to protect the driver & the rear windshield from any part of the load entering the cab.

The headache rack on this truck is circled in red.

With that information, I was ready to get to work (6.17.16):

OK. I’ll work on getting you an answer.

A few days later (6.21.16):

I apologize for my delay in responding. I have an answer for you.
49 CFR 172.504(a) requires placards to be displayed on each side and each end of a transport vehicle such as your 1-ton truck. 49 CFR 172.516(a) requires a placard to be clearly visible from the direction it faces, except for the direction of another transport vehicle (i.e. a tractor trailer combination where the placard on the front of the cargo trailer or tank is blocked from view by the tractor). There is no mention in the regulations of your specific situation. However, a letter of interpretation by the USDOT (LOI 09-0055) does address your issue. it reads, “Generally, placards on the sides and ends of the cargo-carrying portion of a vehicle’s cargo body satisfy requirements for placarding the sides and ends, even if they are not located at the outer perimeter of the vehicle, as long as they are readily visible and not obscured by appurtenances in the direction they face.”
A combination of the above-cited regulations and the LOI should suffice as proof that the method of mounting the placard as you propose is compliant with USDOT regulations.

I hope this helps.

Thank you and please contact me with any other questions.

And, once again, another question answered for someone that I may never hear from again (6.21.16).

Thank you for your help.