When we drive into Portland from Hillsboro, we see two signs apparently prohibiting “HM.” We’ve tried to guess what these signs could mean, with the most entertaining guess being that Hannah Montana isn’t welcome in Portland.
The Manual on Uniform Traffic Control Devices comes to the “rescue”:
On routes where the transporting of hazardous material is prohibited, the Hazardous Material Prohibition (R14-3) sign (see Figure 2B-21) may be used.
Nope, that’s not as much fun. :-p