MUTCD W20-4: ONE LANE ROAD Sign
The W20-4 sign is covered in Section 6H.06 of the Manual on Uniform Traffic Control Devices, 11th Edition. Below are the provisions from that section that describe when the sign is used and how it is placed.
What it means and when it is used
- Standard · Required (shall)The ONE LANE ROAD (W20-4) sign (see Figure 6H-1 ) shall be used only in advance of that point where motor vehicle traffic in both directions must use a common single lane (see Section 6E.01).
- Option · Permitted (may)The distance legend may be either XX FEET, XX MILES, or AHEAD.
Where to read the rest
- Full text: MUTCD Section 6H.06: ONE LANE ROAD Sign
- Mounting height, lateral offset and retroreflectivity for any sign: MUTCD sign placement guide
Source: Manual on Uniform Traffic Control Devices, 11th Edition (Federal Highway Administration, December 2023, public domain). Excerpts are shortened and shown out of context; read the full section before specifying a sign. Your state may still be operating under the 2009 edition or a state supplement. Official manual: mutcd.fhwa.dot.gov.