Editing Automatic Warning System (section)

===AWS at signals===
As the train approaches a signal, it will pass over an AWS magnet. The AWS visual indicator ('sunflower') in the driver's cab will change to ''all black''. If the signal being approached is displaying a 'clear' aspect, then AWS will sound a bell tone (modern trains have an electronic sounder that makes a distinctive 'ping') and leave the 'sunflower' black. This AWS clear indication lets the driver know that the next signal is showing 'clear' and that the AWS system is working.

If the next signal is displaying a restrictive aspect (e.g. caution or stop) the AWS audible indicator will sound a continuous alarm. The driver then has approximately 2 seconds to press and release the AWS acknowledgement button (if the driver keeps the button held down, the AWS will not be cancelled).<ref name="Awsrules"/> After pressing the AWS acknowledgement button, the AWS audible indicator is silenced and the AWS visual indicator changes to a pattern of black and yellow spokes. This yellow spoke pattern persists until the train reaches the next AWS magnet and serves as a reminder to the driver of the restrictive signal aspect they passed.

As a [[fail-safe]] mechanism, if the driver fails to press the AWS acknowledgement button for a warning indication in sufficient time, the emergency brakes will automatically apply, bringing the train to a stop. After stopping, the driver can now press the AWS acknowledgement button, and the brakes will automatically release after a safety time out period has elapsed.