Each state modifies this slightly but not much. Note too that the MUTCD can be your friend if you get a questionable traffic ticket. If the relevant signs don’t

Each state modifies this slightly but not much. Note too that the MUTCD can be your friend if you get a questionable traffic ticket. If the relevant signs don’t follow the standards that’s often grounds for dismissing the ticket. Non-standard signage can be quite common in some jurisdictions, although typically off the Interstates which are more tightly regulated.