MUTCD R4-9: STAY IN LANE Sign
The R4-9 sign is covered in Section 2B.40 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
- Option · Permitted (may)A STAY IN LANE (R4-9) sign (see Figure 2B-10) may be used on multi-lane highways to direct road users to stay in their lane until conditions permit shifting to another lane.
- Guidance · Recommended (should)If a STAY IN LANE sign is used, it should be accompanied by a solid double white lane line(s) to prohibit lane changing.
Where to read the rest
- Full text: MUTCD Section 2B.40: STAY IN LANE Sign
- Minimum sign sizes by roadway type are in the size section for this chapter: Section 2B.03
- 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.