Stop Sign Ahead Sign: When W3-1 Is Required, Size and Distance
Updated · By the Cone to Curb editors
The stop sign ahead sign is the MUTCD's Stop Ahead (W3-1): a red octagon under a black arrow on a yellow diamond. It's required when drivers can't see the STOP sign itself from far enough away to stop for it, and it's optional elsewhere for extra emphasis. The standard size is 30 x 30 inches on conventional roads and 48 x 48 on expressways and freeways.
| Road | W3-1 size |
|---|---|
| Conventional road, single lane each way | 30 x 30 |
| Conventional road, multi-lane, posted 35 mph or less | 30 x 30 |
| Conventional road, multi-lane, posted above 35 mph | 36 x 36 (Section 2C.03 minimum) |
| Expressway | 48 x 48 |
| Freeway | 48 x 48 |
| Minimum | 30 x 30 |
Sizes in inches, from MUTCD Table 2C-1 and Section 2C.03.
When it's required
Section 2C.35 makes the W3-1 mandatory on an approach to a STOP sign that "is not visible for a sufficient distance to permit the road user to respond." Typical reasons: a hill crest, a curve, a bridge or building, trees or parked cars. If the view is blocked only some of the time (summer foliage, parked trucks), the agency decides with engineering judgment.
The sign is also allowed where the STOP sign is visible but the agency wants more warning, for example on a fast rural road meeting a new four-way stop.
How far ahead
Table 2C-3 gives the advance distance for a "potential stop" warning, based on stopping sight distance:
| Speed | Distance ahead of the STOP sign |
|---|---|
| 25 mph | 155 ft |
| 30 mph | 200 ft |
| 35 mph | 250 ft |
| 40 mph | 305 ft |
| 45 mph | 360 ft |
| 50 mph | 425 ft |
| 55 mph | 495 ft |
| 60 mph | 570 ft |
Use the posted speed or the 85th-percentile speed, whichever the agency uses.
Options
- Beacon or LEDs. A Warning Beacon above the sign, or yellow LEDs in the border, may be added (2C.35).
- Distance plaque. An XX FEET plaque below the sign helps where the STOP sign is just past a curve.
- Street name plaque. An advance street name plaque can identify the cross street (Section 2C.65).
Yield Ahead (W3-2) and Signal Ahead (W3-3) follow the same rules and sizes. Signal Ahead is required when drivers can't keep at least two signal faces in view for the distance in Table 4D-2.
Mistakes we see
- Placing it right before the stop. Drivers need the full table distance to react and brake.
- A 30-inch sign on a fast multi-lane road. Above 35 mph, multi-lane roads need 36 inches.
- Fixing a blocked STOP sign with only a Stop Ahead. Trim the trees or move the STOP sign too, if you can.
What it costs
Ballpark U.S. prices in late 2026: $45 to $110 for a 30-inch W3-1 with high-intensity sheeting, $70 to $160 for 36-inch, more for prismatic sheeting or LED-embedded signs ($600 and up).
Where to buy
Sign shops and traffic safety distributors. Ask for the code (W3-1), size, sheeting type and, for LED signs, the power source and flash pattern.