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Saturday, August 8, 2020

Class investigation into signalling operation

RAIB has investigated the effects on human performance in signalling operation following “numerous incidents in which signaller decision-making has been pivotal”

The work of signallers, hidden away in signal boxes and control centres, is sometimes taken for granted. Now the Rail Accident Investigation Branch (RAIB) has published a report entitled “Class Investigation into human performance in signalling operation”, which includes six recommendations.

Signalling, like the rest of the railway’s operating equipment and infrastructure, has come a very long way recently. Nowadays, many signallers work, not in lineside signal boxes, but in signalling centres with as many as fifteen computer workstations in front of them. The skills needed have also evolved, but RAIB has recommended that still more needs to be done.

RAIB report 03/2020, published on 12 May, states that railway safety is heavily dependent on signallers’ decisions and lists five categories of incident where those decisions sometimes aren’t up to standard – user-worked crossing irregularities, line blockages, users trapped on CCTV controlled crossings, irregularities involving level crossings on local control and “other operational irregularities”. The class investigation examined and reviewed a number of case studies, selected from each of the five listed categories.

Example of a signalling centre with control panels (Nottingham Trent).

User-worked crossing incidents most often involved signallers giving permission to cross to members of the public as a train was approaching. Line blockage incidents reviewed included granting a line blockage on a section of track with a train already in it or signalling a train into a blockage.

With CCTV-controlled crossings, there were incidents of signallers clearing signals whilst a user (most often a pedestrian) was on the crossing. At crossings under local control, most incidents were of trains passing over crossings whilst the barriers were raised.

500 signal “boxes”

Network Rail operates approximately 500 signal boxes nationwide. Signalling centres/boxes are broadly of three types: lever frame, signalling centres with control panels and centres with computer workstations. (See photographs of typical layouts/arrangements). Whilst most of the computer centres have five workstations, some have as many as fifteen. In total Network Rail employs around 5,200 signalling staff.

A number of common factors were identified, including signaller workloads, user centre design, competence management, experiential knowledge and organisational structure. The report also states bluntly: “Network Rail’s investigations do not always fully exploit the opportunities to learn from these incidents.”

Recommendations from RAIB

The RAIB report makes six recommendations, which may be summarised as follows:

  1. Network Rail should develop improved techniques for measuring and predicting cognitive workload and integrate such techniques into the management of signaller workloads;
  2. Network Rail should review its processes to incorporate a user centred approach to changes in signaller workload and the review should include ergo-dynamic design;
  3. Network Rail should develop and support those delivering training and assessment of signallers at local level and include ‘train the trainer’ coaching guidance;
  4. Network Rail should research the experiential knowledge of experienced signallers and learn how such knowledge contributes to performance;
  5. Network Rail needs to implement measures in the National Operations Programme and revise management to ensure that those supervising and managing signallers have the time, skills, knowledge and status so that they may undertake their roles effectively;
  6. Network Rail should review, modify, and/or reinforce processes for the investigation of incidents. Specifically, they should use a ‘fair culture’ flowchart and analysis of underlying factors using a wider trend analysis to identify systematic issues. Additionally, they need to achieve full separation of safety investigations from the disciplinary process.
Example of a lever frame signal box (Bury St Edmunds)

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