MUTCD W24-1: Double Reverse Curve Signs

The W24-1 sign is covered in Section 6H.31 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)
  The Double Reverse Curve (W24-1, W24-1a, or W24-1b) sign (see Figure 6H-1) may be used where the tangent distance between two reverse curves is less than 600 feet, thus making it difficult for a second Reverse Curve (W1-4 series) sign to be placed between the curves. If the design speed of the curves is 30 mph or less, Double Reverse Turn signs may be used.
• Standard · Required (shall)
  If a Double Reverse Curve (or Turn) sign is used, the direction of the double reverse curve (or turn) shall be appropriately illustrated. Except as provided in Paragraph 3 of this Section, the number of lanes illustrated on the sign shall be the same as the number of through lanes available to road users.

Where to read the rest

• Full text: MUTCD Section 6H.31: Double Reverse Curve Signs
• Mounting height, lateral offset and retroreflectivity for any sign: MUTCD sign placement guide