Hazardous Material Prohibited
- Shape
- Square
- Color
- Red circle and slash over HM
- Meaning
- Vehicles carrying hazardous materials are prohibited.
- Required driver action
- If placarded, do not enter; use an approved route.
- CDL relevance
- Often posted before tunnels and some bridges.
Source: FHWA — Manual on Uniform Traffic Control Devices (MUTCD) (11th Edition (December 2023)). Sign images are original simplified illustrations for study, not official MUTCD artwork.