Background

A number of systems used in driving cabs present warnings to drivers either for advice or to indicate a need for specific action. Such warnings are essential to the safe and efficient delivery of the driving task.

Over the years the number of warnings presented to drivers has grown as new systems have been introduced, for instance the Driver's Reminder Appliance and Train Management Systems. It is within this context that the Vehicle/Train Control & Communication System Interface Committee (V/TC&C SIC) is seeking opportunities to see how these disparate systems can work better together, leading to realisation of what the driving cab of the future might look like in this respect.

As a first step in this process, it was recognised that there has already been a range of research undertaken in relation to individual cab warnings and how they work as a group. V/TC&C SIC therefore endorsed a review of published and ongoing research which was relevant to the rationalisation of drivers' warnings in the train cab.

Aims

The aims of this project were to review existing research literature and existing train cab designs in order to provide:

* A baseline of the systems and their associated warnings that are present in Britain’s existing railway cabs.

* A baseline of the knowledge that is currently held by the rail industry and the human factors disciplines with regard to in-cab systems and their warnings.

* Indication of options for rationalisation of cab warnings.

* Key learning points and/or functional requirements for the future design of warnings.

The scope of cab warnings considered in the review was audible and visual discrete change of state information which supports drivers in the driving task.

Methodology

On behalf of RSSB, Gibson Ergonomics Limited reviewed literature collected from RSSB and the Ergonomics Information Analysis Centre. Meetings were held with people involved in ongoing projects related to drivers' warnings, in particular the European Rail Traffic Management System (ERTMS).

In addition, a survey of cab warnings was undertaken for the following cabs, in order to develop a baseline of current systems.

The reviews were undertaken for:
* Virgin Pendolino
* Virgin Super-Voyager
* Silverlink Class 508
* Silverlink Class 313

The key output from the work is a summary and synthesis of the available literature.

Findings

The literature reviewed is quite rightly dominated by the key safety devices which provide warnings to the driver. These systems include the Automatic Warning System (AWS), Driver’s Reminder Appliance (DRA), Train Protection and Warning System (TPWS), Vigilance Device (VD) and Driver Safety Device (DSD).

Specific companies also use Automatic Train Protection (ATP), Tilt Authorisation and Supervision System (TASS) and Tripcock Systems.

The review identified that the set of protective devices available in the current driving cab represents a series of in-life upgrades and that this is unlikely to produce a very satisfactory or coherent situation from the users' perspective.

Rationalisation of drivers' warnings in the cab could therefore be considered in order to:
* Reduce confusion between different warnings.
* Reduce driver workload and the risk of driver error for tasks which are not directly related to train control.
* Increase available display space in the cab.
* Simplify maintenance.
* Simplify training.
* Improve safety and performance (for example, through reducing the number of driver errors and train brake demands).

In the context of routine driving, cab warnings are inextricably linked to a number of driver safety devices, such as the AWS. In this context the safety devices themselves could be rationalised. All the safety devices aim to ensure the train does not exceed movement authorities or travel too fast. One system which can do this across all situations would be the most direct step to rationalisation and realising the benefits listed above. Removal of individual warnings could also be considered for individual devices; for example, the VD audible warning could be replaced with a physiological monitoring system.

The other key area which is open to rationalisation is warnings related to activation of drivers' safety devices and train-related faults. As for routine driving, the adoption of a single safety device would also rationalise warnings related to safety device activation.

There are necessarily going to be a large number of faults which need to be reported and associated warnings must be in place in the cab for the driver. It is critical that faults which can be presented to the driver while the train is in motion provide minimal distraction to the driving task. The strategy of stopping the train for critical faults is clearly required and in these situations rationalisation could be achieved by designing the fault presentation from a driver rather than an engineering perspective (for example, indicating the R&D Programme: Research Brief tasks which are required to rectify the fault or the information to be reported to maintenance staff, rather than a direct indication of a specific engineering fault). The strategy of a single alarm to warn of all critical faults, as seen in more recent cab designs, is also of value.

It should be noted that cab warning rationalisation is only one element in the wider design of the driving task. For example, significant questions relate to increasing automation of the driving task, and this automation will lead to impacts on cab warning philosophies, as well as impacts on other factors such as the speed of driver reactions to safety critical events.

Rationalisation should not be pursued to the extent that new warning information which would be valuable to drivers is excluded. For example, drivers have requested information on the status of traffic in front of the train and assistance with station duties and station stops. It may also be appropriate to provide further warnings related to the status of safety critical systems, in particular for some TPWS failures during service.

Next Steps

This research confirms the importance of a system based approach to provision of driver' warnings. As devices are added to cabs, the impact on the driving task must be considered in conjunction with the impact of other existing devices so as to minimise the risk of driver distraction and service disruption

In considering the findings of this work, the industry's Vehicle/Train Control & Communication System Interface Committee has discussed the benefits of rationalising drivers' warnings and has concluded that the emergence of interoperability legislation means that rationalisation for future cab designs should be progressed within a European context. RSSB, working with key stakeholders, is involved in several relevant pan-European projects, such as Modtrain, and will use the findings from this work to inform these projects, which will in themselves inform future European standards.

Contact
Head of Engineering Research
Research and Development Programme
Rail Safety and Standards Board research@rssb.co.uk