The FHWA recently posted proposed changes to the MUTCD. A call for comments has been issued and ADOT is in the process of reviewing the proposed updates. If you are interested in providing comments please reach out to webmaster@itsaz.org. Comments are due to Hasina Luna (hluna2@azdot.gov) no later than 26 February 2021.
A link to the proposed changes can be found here – https://beta.regulations.gov/document/FHWA-2020-0001-0038. Thank you for your time in this process!