Suter, J.; Stoller, N.:
Use of simulators to investigate complex issues at the human-machine interfaces (HMI) of railway systems.
First German Workshop on Rail Human Factors 2014, Braunschweig, Deutschland, May 2014.
Technological developments and increases in rail traffic are resulting in ever more complex rail systems.
This involves, among other things, automating and improving certain processes. The automation of the
HMI in the drivers’ and the train dispatchers’ environments has taken different forms, depending on the
It is often difficult to investigate in any depth the problems arising at the interface between people and
machines, known as human-machine interface (HMI), because many of the influencing factors cannot be
measured discretely and the context is not always clear. At the same time, the demands placed on the
staff who manage rail operations are growing as a result of the increase in automation, which places
greater responsibility on a smaller number of people. Train dispatchers and train drivers are directly affected
by these changes. For this reason, findings in areas such as the stress and workload limits of staff (human
factors), the user friendliness of controls (usability engineering) and the causes of inappropriate behaviour
and operator error are becoming increasingly important in risk assessment. Understanding the
complexity of these requirements can improve safety levels across an entire rail system.
In order to investigate these issues, a set of specific problems for rail operators are devised that cannot be
evaluated using linear methods because of their complexity. These are typically situations where the development
is directly dependent on the perception and the decision-making behaviour of the driver and
the train dispatcher, and which cannot be determined in advance with complete certainty. The problems
give rise to objects for investigation which are subjected to as many repetitions as possible by the test
subjects on the integrated realistic simulation models. The only full simulator available in Switzerland – of
a type Re 460 locomotive – is used for the tests. The findings from these tests are evaluated together with
additional data that have been acquired using qualitative methods (systematic questioning of the test
One such problem is the signal passed at danger (SPAD), which occurs when a driver passes a stop signal
without the authority to do so. These cases involve complex human-machine interactions with influencing
factors that are difficult or impossible to quantify. It is, however, possible to survey a representative sample
by running simulations with test subjects (train drivers and train dispatchers). This gives rise to the
question of how the level of detail and the realism of the models influence the behaviour of the test subjects
and, therefore, the results of the investigation.
The aim of this research study is to gain a better understanding of the railway as a complex sociotechnical
system by proposing an approach to modelling as the basis for integrated simulations. Using
driving and signalling simulators, it has been possible to obtain findings concerning both the necessary
level of detail of the models and the requirements for integrated simulation models used to investigate
HMI.. Specific problems and objects for investigation are used to explain how the