As far as I can tell despite all the supposed great progress in signal automation and upgrading associated with for instance the signal work allegedly being done during the current two week long blockade of all Southern trains running in to London Victoria a great many of these unnecessary waits at red signals are associated with train paths to further down the line having not yet been set by the signal control room before the arrival of the relevant train at the relevant signal. Hence the train concerned is backed up at that red signal until the relevant signal room or signalman sets that train path, perhaps after they have made themselves their next cup of tea........
Hence many trains waiting at red signals seems to be caused by train pathing still not being sufficiently automated or pre-planned even though of course some red signal delays are caused by men working on the track, youths walking on the line or congestion further up the line caused by a defective train or a passenger on the line. However the information that a train is not proceeding any further just because it is at a red signal is inherently unsatisfactory given that it was self evident all along that was the case but the information is more or less useless without further information as to the cause of the signal being at red rather than at green, amber or double amber..............
Railway signals designed for displaying aspect to train drivers don’t have amber or double amber aspects. Only red, yellow, double yellow and green main aspect, or white for shunting, crossing indicators, route or junction indicators, banner indicators, off indicators and some other specific signals.
The only railway signals that have amber aspects/lamp assemblies are road traffic lights at level crossings.
With controlled signals, their normal state unless routed is red. With automatic signals, their normal state (assuming there is no train in the section that they protect) is a proceed aspect (yellow, double yellow or green depending on the aspect of the next signal).
No signaller intentionally keeps a signal red for a train. If a signal is red, there is normally a VERY good reason for it.
On the approach to large stations, one problem can be that the scheduled platform is not available due to a late running train occupying it. The signaller can’t normally just pick a random empty platform. The station staff and the signaller and maybe control have to agree which alternate platform (if any is available) will be used.
I live very far from DOO land. Hence the vast majority of announcements are made by the guard/train manager/(whatever other name the TOC is using this week). This person will normally not know the reason that the train is being held, or the reason for the delay until either the driver has been told and then passed the information on. Or they receive the information from control.
The driver is not permitted to be distracted while driving. So unless it is an emergency, drivers are not contacted to inform them. Signallers wait for them to call them.
Unless otherwise indicated (written instructions or sign fitted to the signal or verbal instruction from earlier from a signaller), drivers will wait the (standard) two minutes at a red signal before calling the signaller (as per the standing rules). - EDIT: It appears the relevant rules have changed since I last read the section where this was. See the reply later in this topic.