"Advanced Warning Lights" (AWL) is an active device, incorporating twin flashing amber aspects mounted on a pole. Positioned in between the pair of flashing amber aspects, is a "Prepare to Stop" information sign. On top of the amber aspects, is a "Traffic Light Ahead" sign.

AWL is generally installed before a traffic junction or a signalised pedestrian crossing, which may not be visible to motorists due to road geometries.

They warn motorists in advance to a red traffic signal and that they need to prepare to stop. The lights would start flashing three seconds before the downstream traffic signal turns amber. They would continue flashing until the end of the red signal.

Hence, when the lights on AWL are flashing, motorists should get ready to stop before the stop line at the traffic junction or pedestrian crossing. When the lights on AWL are not flashing, motorists should slow down in anticipation of the traffic junction or pedestrian crossing in front. They may proceed only when it is safe for them to do so.

The AWL is therefore a useful device to advise motorists of the change in signal phasing at the downstream (obscured) traffic signals.