Where Should “Road Work Ahead” Signs Be Placed?
Published
Introduction
No matter the roadway, active road work usually interrupts its typical traffic flow. MUTCD standards require Work Zone Signs to keep drivers informed at every point along the way, and the W20-1 Road Work Ahead Sign is likely the first Work Zone Sign drivers will see. We’ll take a look at where to install the W20-1 and the other Work Zone Signs that often follow.
What Types of Work Use Road Work Ahead Signs?
In general, any work area that is located in the road or on roadsides needs advance warning, such as when the following work is being performed.
Roadway and paving work
- Asphalt paving – laying down new asphalt or refreshing existing roads
- Milling operations – removing a layer of a paved surface or its entirety
- Resurfacing – adding a new top layer onto an existing road
- Striping projects – repainting faded lane lines and road markings
Roadside construction
- Shoulder repairs – restoring the structure of a road shoulder
- Guardrail installation – adding a protective guardrail along a roadway
- Drainage work – cleaning or rebuilding a roadside drainage system
Utility-related roadway work
- Water line repairs – responding to interruptions in water services
- Sewer work – maintaining the sewer system infrastructure
- Electrical or fiber installation – setting up a new utility system
When road work is 15 ft. or more from the shoulder, signs may be helpful but it isn’t usually needed (6N.05, 01).
When Other TTC Signs May Be More Appropriate
Road Work Ahead Signs have the most general messaging out of the many temporary traffic control (TTC) warning signs available. At times, construction projects may need signs with more specific messaging, such as:
Specific signage is especially useful when work activity can impact or interrupt traffic flow. Drivers need to know the exact situation ahead and if they need to take any actions.
Where Road Work Ahead Signs Should Be Placed
For work zones, sign spacing and placement generally depends on four factors: roadway speed, visibility, road type, and work zone complexity. Engineers can use this information to adapt signage to a project’s field conditions.
| Road type | Distance Ahead |
|---|---|
| Urban roads | 4-8x the speed limit |
| Rural roads | 8-12x the speed limit |
| Freeways | ½ mile or more |
Roadway speed
The greater the road’s traveling speed, the longer an “advance warning area” should be. Within each category, Section 6B.04 recommends more distance as the speed limit increases:
| Road | Speed limit | Distance to the sign nearest the work |
|---|---|---|
| Urban | 25 mph | 100 to 200 feet |
| Urban | 35 mph | 140 to 280 feet |
| Urban | 45 mph | 180 to 360 feet |
| Rural | 45 mph | 360 to 540 feet |
| Rural | 55 mph | 440 to 660 feet |
| Rural | 65 mph | 520 to 780 feet |
Visibility
When sight distance is limited because of curves or obstructions in the road, additional signs might be needed (6H.02, 03)
Road type
Whether the road is urban, rural, or an interstate, the recommended minimum spacing between signs varies. Table 6B-1 recommends how far apart Advance Warning Signs should be spaced.
| Road Type | Distance between Signs** | ||
|---|---|---|---|
| A | B | C | |
| Urban (low speed)* | 100 feet | 100 feet | 100 feet |
| Urban (high speed)* | 350 feet | 350 feet | 350 feet |
| Rural | 500 feet | 500 feet | 500 feet |
| Expressway / Freeway | 1,000 feet | 1,500 feet | 2,640 feet |
* Speed category to be determined by the highway agency or owner of site roadways open to public travel.
** The A dimension is the distance from the transition or point of restriction to the first sign. The B dimension is the distance between the first and second signs. The C dimension is the distance between the second and third signs. The “first sign” is the sign in a three-sign series that is closest to the TTC zone. The “third sign” is the sign that is furthest upstream from the TTC zone.
Work zone complexity
The more complex the work zone, the more signage is usually seen in the TTC advance warning area.
Typical Advance Warning Sign Sequence
Whenever more than one TTC warning sign is being used, the Road Work Ahead Sign should be the first in the sign sequence. An example TTC sign and device sequence from Figure 6P-33 includes:
- Road Work Ahead Sign
- Right Lane Closed Ahead Sign
- Right Lane Ends Symbol Sign
- Channelizer Drum Taper
- Work Area
- End Road Work Sign
Predictability in sign order makes work zone messaging effective—and roadways safer.
State and Local Requirements
Following official requirements on the federal, state, and local level is key before setting up signs. Traffic agencies may require a permit and traffic control plan that complies with their preferred:
- TTC sign sequences
- Spacing distances
- Work zone layouts
- Reflective sign materials
The best signs for advance warning are clear, project-specific, always in a driver’s sightline, and visible at both day and night.
Conclusion
A Work Zone Sign system heavily depends on a project’s needs. Repaving, shoulder work, or any other road work can call for very different MUTCD signs. In many cases, the multi-purpose Road Work Ahead Sign leads a series of advance warning signs. And in some advance warning areas, it’s all the signage that’s needed.
