Train Dispatch and Preventing Start Against Signal SPADs

A Start Against Signal SPAD occurs when a train proceeds from a stand towards a signal and passes it at danger. This type of SPAD can occur if when at a station the driver is inadvertently given an indication by station staff, or the guard, that platform duties are complete. If the driver does not check the signal before proceeding, a SPAD will result.

Research into dispatch risk demonstrates the risk of collision from Start Against Signal SPAD (SAS-SPAD) due to train dispatch is minimal. This is because errors from both the driver and person dispatching the train must happen for a SAS-SPAD to occur. SAS-SPADs are a problem because the signal may not be fitted with Train Protection & Warning System (TPWS), and if the driver is not aware of the signal aspect, they may continue taking power after the SPAD.

Research has identified that the interaction between dispatch method, technology and personnel can make SAS-SPADs more likely:

  • Drivers and guards might have to use a variety of dispatch methods along a route and sometimes this leads to uncertainty about which applies. Any confusion might lead to the signal aspect check being missed. This can be worse where stations are staffed part-time, meaning that the dispatch method would change based on staffing arrangements.
  • Platform staff may also have to switch between dispatch methods depending on the type of rolling stock coming, and so there is a chance that the wrong method may be used.
  • Platform staff are susceptible to being distracted by passengers on the platform. Such distractions may lead to them forgetting where they were in their dispatch sequence, and possibly result in an erroneous indication being given to the driver.
  • Frequent use of the bell-buzzer by guards to give a ready to start indication may mean that the buzzer is used at a station when a Right Away indicator should be used.
  • Right Away indicators can prevent drivers being told that the train is ready to start against a red signal, as they are interlocked with the signalling.

Clearly most of the responsibility for managing SAS-SPAD risk rests with drivers checking the signal aspect and correct use of the Driver’s Reminder Appliance. The following measures should help others contribute towards managing SAS-SPAD risk:

  • Identifying where risks lie on a route and checking whether dispatch arrangements are optimised, in terms of dispatch consistency, for all those involved.
  • Confirming ‘check signal aspect’ boards are in place on at-risk signals.
  • Ensuring dispatcher training and briefings addresses the risk of using the wrong dispatch method, this should underline the need for extra vigilance and checking.
  • Use of Risk Triggered Commentary by dispatchers, supported with a staff booklet and a booklet for managers.

The guidance document on guard’s route knowledge (T1151 GPG) covers dispatch methods and identified the following as a core requirement:

'For each platform stopping position, any visible signal which applies and what indicator is needed (including platform starting signals, junction indicators, OFF indicators, banner repeaters, and TRTS buttons). Knowledge must include: signal type, the position, sighting.'

The document is consistent with the forthcoming Railway Industry Standard (RIS) which covers guards’ route knowledge (RIS-3702-TOM). To help make sure guards have the necessary route knowledge, the document also explains how a ‘route story’ approach can be used to good effect.

Route story approach

Route story is the name for the new approach to route learning. A route story defines route knowledge requirements as a sequential list of route cues. It details what the learner needs to know about each one. This is done for each line on a route—up and down, fast and slow, and any diversions. It should be the minimum set of route cues needed for safe operation in a role (train driver or guard) over a route. The route story covers both route cue information (like junction speeds and station names) and route risks (like irregular signal spacing) needed for task competence, in both normal and degraded modes.

Haven’t found what you’re looking for?
Get in touch with our Principal Human Factors Specialist for further information.
Philippa Murphy
Tel: 020 3142 5641
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