Traffic Signals and Authorised Official Commands
What this domain covers
Traffic signals and controller commands are at the top of the control hierarchy. The exam tests light sequences, arrow signals and the meaning of a traffic officer's posture.
Traffic lights
- Red: stop before the stop line or crossing.
- Yellow: stop unless stopping would be unsafe; flashing yellow means proceed with caution.
- Green: proceed if the way is clear; a green arrow permits movement in that direction.
- Red plus yellow: prepare to start, but do not enter the junction until green.
- A green arrow with a red main light allows movement only in the arrow direction, giving way where required.
Controller signals
- Arm raised vertically: all road users stop.
- Arms outstretched to the sides or lowered: traffic on the controller's left and right may proceed under the usual movement rules.
- Right arm extended forward: traffic facing the controller's chest must stop; traffic from the controller's right may proceed.
- The whistle draws attention; the posture, not the whistle, is the order.
Worked example
A green light shows, but the officer has raised a baton. The driver stops at the stop line. Priority is controller > light > sign > marking, so the raised baton cancels the green permission.
Traps
- Starting on red plus yellow.
- Treating a flashing yellow as a green light.
- Obeying the light while a controller is directing traffic.