rail accidents happen 'human error' is often blamed. Paul Salmon argues
that in order to understand what's gone wrong, the whole system must be
tragic events at Kerang, a rural town in Australia, on the 5th June
2007 demonstrate the importance of optimising road users’ situation
awareness at rail level crossings. Here, the driver of a loaded truck
continued toward a rail level crossing, unaware that a passenger train
was also approaching. The resulting collision killed 11 train passengers
and injured a further 15 people, including the truck driver.
an exhaustive investigation into the incident, the Office of the Chief
Investigator concluded that the train and train crew, the truck, the
road and rail infrastructure, and the rail level crossing warning
devices all played no causal role in the incident. They commented that,
“For reasons not determined the truck driver did not respond in an
adequate time and manner to the level crossing warning devices”. The
truck driver was subsequently prosecuted on the basis that he had failed
to keep a proper lookout. He pleaded not guilty to eleven counts of
culpable driving causing death and eight counts of negligently causing
serious injury and was acquitted by a jury. The rail level crossing
involved was subsequently modified to include boom gates, Light Emitting
Diode (LED) lights, rumble strips, and active advanced warning signs.
With terms such as ‘human error’
often bandied about in the aftermath of such incidents, it is tempting
to think that the road user is the broken component that creates rail
level crossing collisions and that the rest of the road and rail
‘system’ works just fine. However, current ergonomics thinking would
suggest that there is more to the problem of degraded road situation
awareness at rail level crossings. The aim of this article is to
demonstrate, through deeper examination of the contributory factors
involved in the Kerang tragedy, the role of wider systems failures in
rail level crossing collisions.
The individual psychological explanation
an individual level it is clear that the truck driver was unaware of
the approaching train and of the flashing lights at the rail level
crossing. There is no suggestion that the driver was impaired through
distraction, fatigue, alcohol or drugs, or that he wilfully attempted to
beat the train through the crossing. Using Neisser’s perceptual cycle
model to explain the truck driver’s behaviour, one plausible explanation
is that the truck driver’s failure to see the flashing lights was
caused by a schema-driven looked-but-failed-to-see error whereby he
scanned the rail level crossing’s warning lights, but did not perceive
their flashing state. This failure in turn was likely caused by the
activation of the wrong mental schema in the mind of the truck driver,
namely a schema for the level crossing in a non-activated state. The
truck driver had driven trucks along the same route approximately once a
week for seven years prior to the incident but had never previously
experienced a train at the crossing. His previous exposure to the
crossing in a non-activated state shaped his cognition and expectancies
in such a way that he behaved as if a train wasn’t approaching, just as
he had done on numerous previous occasions. The warnings provided at the
crossing failed to override his wrongly activated schema.
The systems explanation
the road and rail system shows that various factors at the equipment
and surroundings level played a role in the truck driver’s failure to
become aware of the approaching train. Although the rail level crossing
had flashing lights, road-based warnings and an early warning sign, it
was not fitted with boom gates which would have provided a more
conspicuous visual cue. At the time of the incident considerable sun
glare may have impaired the driver’s ability to see the crossing warning
signage and controls. The contrast between the train and its background
is likely to have been reduced as a result of the truck-facing side of
the train being shadowed. Trees in close proximity to the left hand side
of crossing may have obscured the truck driver’s vision of the
approaching train while the A-pillar of the truck also provided a
potential momentary obscurement of a stationary vehicle located on the
opposite side of the crossing.
The train driver sounded the horn
twice on approach to the crossing, first at the whistle board, and then,
continuously for 7 seconds from the point at which the train was 140
metres from the crossing. It is unlikely, however, that the first horn
sounding would have alerted the truck driver to the presence of the
train. Finally, the road speed limit at the time of the collision was
100km/h. A lower speed limit could have provided more time for evasive
action once the truck driver became aware of the approaching train.
physical processes and actor activities level of the system covers the
chain of events that led to the truck colliding with the train. Included
at this level is the truck driver’s lack of experience of the rail
level crossing with a train approaching. On the day of the incident the
driver was delayed in departing the depot due to freight loading issues.
This delay ensured that he encountered the crossing at the same time as
the train. From here on, activation of the wrong schema meant that the
driver failed to notice the approaching train, and the crossing’s
flashing light warnings, until it was too late.
loading of the truck is placed at the technical and operational
management level of the system, as is an inspection of the rail level
crossing conducted by an infrastructure manager. This inspection was
undertaken in response to a series of near miss incidents at the
crossing prior to the incident and a letter from the train operator to
the track manager expressing concern over road user behaviour at the
It is apparent that the haulage company involved was not
aware of the near miss incidents, a fact that is placed at the local
government and company management level of the system.
regulatory bodies, state government and industry level various factors
combined to ensure that the crossing was not upgraded to include boom
gates. On the basis of the near miss incidents and letter to the track
manager, various activities were initiated, including public education
efforts and the addition of the crossing to the state government’s rail
level crossing upgrade prioritisation list. As a result, the crossing
was assessed the year before the incident using the Australian Level
Crossing Assessment Model (ALCAM). It was assigned a risk score and was
ranked 140 out of 143 rail level crossings on the prioritisation list,
meaning it was not upgraded at the time of the incident.
associated with the ALCAM tool are placed at the Government/Parliament
policy and budgeting level. Although ALCAM provides a risk assessment
score for different rail level crossings, there are various issues that
raise questions over its utility. For example, it does not currently
take into account accident or near miss data or data on human
performance and is heavily weighted towards exposure data, that is, the
volume of road and rail traffic passing through the rail level crossing.
These limitations means that rail level crossings such as Kerang, which
have a low road and rail traffic volume, typically achieve lower risk
scores than high traffic rail level crossings. In addition, financial
and budgetary constraints limit the number of rail level crossings that
can be upgraded to full active controls.
Taken together the
individual psychological explanation and the systems explanation
demonstrate that road user behaviour at rail level crossings is an
emergent property of complex sociotechnical road and rail systems. In
the case of Kerang, although the driver’s degraded situation awareness
was the key causal factor, there were multiple interacting upstream
factors that played a role in this degradation. The tragic incident was a
systems accident driven by contributory factors across all levels of
the road and rail system. The following are key messages for
practitioners attempting to enhance safety at rail level crossings:
Multiple interacting factors shape the behaviour of road and rail systems.
is a shared responsibility for rail level crossing safety across
multiple actors and organisations. A shift away from individual blame
and culpability to a learning culture for system improvement is needed.
This shift can only occur when the complexities of human behaviour and
the impact of the system on behaviour is understood. Modifying rail
level crossing infrastructure alone will leave other behaviour-shaping
factors free to play a role in future incidents.
By Paul Salmon, Associate Professor in the Faculty of Arts and Business at the University of the Sunshine Coast, Queensland, Australia.
This article was first published in issue 521 of The Ergonomist, November 2013.