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AWS Warning


The Automatic Warning System, abbreviated to AWS is a system that was originally designed to reduce the probability of a SPAD after an APT introduction was decided against. On the passing of the AWS sensor, either a bell/electronic ping or audible beep is played in the cab alerting the driver of the aspect ahead. On a decrease in line speed of more than 1/3, AWS is legally required to be fitted at a signal. SCR has replicated this by permanently setting some signals to Caution (single yellow) or Danger (red). There is a speed limit of 45 upon passing a single yellow (caution) signal.

Operational Use

In SCR, the driver will pass over a yellow sensor, which is an AWS ramp. If the signal aspect is not displaying a proceed (green) aspect, a loud beep is heard. To cancel the beep, drivers must press the Q button or click the yellow exclamation mark in the GUI that comes up to cancel the warning, therefore silencing the beep. However, if the next signal displays a green (proceed) aspect a bell (always an electronic ping in SCR) and the driver is not required to take any action. In SCR, an AWS warning is only played if the next signal is Preliminary Caution, Caution or Danger. A Caution aspect is placed at some speed restrictions to trigger a warning. For example, this is the case at Coxly station approach where the speed limit decreases. When a driver does not take any action against the AWS warning, a red alert 'Driver Alert Ignored' shows up and the emergency brakes are applied for 10 seconds. The AWS doesn't warn you for speeding, this role is played by TPWS which was a system implemented in the 2000s after SPADs were still happening. TPWS is not a system designed to correct common driver failures e.g speeding but to reduce the risk of any signal being passed at danger by stopping trains approaching a danger aspect only at up to 80mph. This is within the standard 800m overlap.

Faults and Failures

AWS was previously mostly realistic - a warning only was ever updated when you passed a signal. In an update where the new next signal GUI was introduced, AWS started warning people of a change of aspect triggering a warning no matter where you were on the track. If the signal in front of you changed you would be warned for this, as with if the signal cleared to a proceed aspect in front of you, unlike real life operation.

TPWS 2000

TPWS is a confirmed feature on the SCR roadmap and it is unclear when it is going to arrive. BanTech - SCR's scripter has said that if there is an update to the signalling system, a TPWS introduction is likely. TPWS/AWS are interlinked systems but are tasked to do very different tasks. TPWS is designed to stop any train approaching a signal at danger that is going too fast to stop at the signal with a real life limit of 80mph with an overspeed sensor and 50mph without to stop within the 800m standard overlap. AWS is the older system that warned the driver about danger signals ahead whether it was 3 signals away (Preliminary caution), 2 signals away (caution) or the next signal (danger).

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