At traffic lights, amber on its own means:

When traffic lights display amber on its own, it signifies that drivers should prepare to stop at the stop line. The purpose of the amber light is to alert motorists that the signal is about to change to red, which requires a complete halt. It serves as a warning to ensure that drivers can safely and predictably respond, promoting road safety.

Drivers must be vigilant and ready to cease movement when amber is displayed, as continuing through an intersection at this stage could lead to dangerous situations, especially if the light changes to red unexpectedly. This understanding of the amber phase is crucial in maintaining traffic order and ensuring the safety of all road users.