Temporary Signals and Automated Flagger Devices
Where traffic on a single open lane must be controlled without a person in the roadway, temporary signals and automated flagger assistance devices (AFADs) can manage the alternating flow.
Last reviewed: June 24, 2026
Why It Matters
- These devices can control alternating traffic while keeping a person out of the immediate roadway, but only when they are set up, timed, and monitored correctly.
- A miscommunicating temporary signal or AFAD can release two directions into one lane — a serious hazard.
When It Applies
- Where one-lane, two-way control is needed and the approved plan and agency allow a temporary signal or AFAD in place of, or with, flaggers.
Planning Considerations
- Confirm the device is permitted for the situation, and plan sighting, timing, and monitoring; specific requirements come from the applicable MUTCD and the agency.
- Plan for backup control if the device fails.
Field Considerations
- Position and time the device so both directions are safely stopped and released, never released together, and monitor it during operation.
- Maintain power and function, and keep queues within the planned limits.
Inspection Considerations
- Inspectors confirm the device controls both directions correctly, is monitored, and has a failure plan.
Common Compliance Failures
- Timing or placement that could release conflicting movements.
- No monitoring or no backup plan when the device fails.
Upstream Prevention
- Verify the device is approved for the situation and plan timing, monitoring, and failure backup.
- Brief the crew on the device's operation and the fallback to flagging.
Related Pages
Relevant Signs on MUTCDSignChart.com
For individual sign codes, meanings, and specifications, see the sister site MUTCDSignChart.com. The signs below link directly to their reference pages:
Official Sources
Frequently Asked Questions
What is an automated flagger assistance device (AFAD)?
An AFAD shows a stop/slow signal or gate, run by a trained worker standing away from the travel lane — so no one has to stand as close to moving traffic. Whether it can be used, and how, is set by the MUTCD, the agency, and the approved plan.
When are temporary traffic signals used in a work zone?
Temporary signals are used to control alternating traffic where a flagger or an AFAD is not appropriate, such as longer one-lane sections. Their use and placement are set by the standard and the approved plan.