Reg - Aspect Step up & Step down

[PJW]

A driver should not see aspects step nor climb down. In the UK (mainline) that would be classed as an abnormal aspect sequence and requires a driver to stop at the next available safe place to report it.

A driver should not see aspects step down in nomal circumstances; it does happen in failure conditions (things need to fail safe) and in emergency. Occasionally a signaller will inadvertantly replace a signal just prior to a train passing it, or when they think the train is far enough away not to see an aspect reversion but misjudges- therefore it occasionally does happen.

Of course drivers should see aspects step up as conditions improve ahead. Otherwise haveing once shown a driver a Red then you are saying we should never show a Yellow or a Green for example!