Accident Theory Analysis

Coaster Collision Case
Continuing the same case as you just diagrammed in Assignment 2, here is the correct diagram
for the boxes provided. The final effect is at the left side, unfolding backwards in time from left
to right. The antecedents of effects include exceptional conditions and events and unexceptional
conditions and events that contributed to or enabled the effects. In addition, the specific design
error (the system provided the ability to manually clear fault from station console without
needing to verify fault on location) is included, at the bottom edge of the diagram.
Coaster Collision
Error exercise (5 points)
Your assistant safety officer has just collected the following information for you from witnesses
and people involved in the case.
The attendant who loaded the cars at the station loaded a group of three slender middle school
children (meeting the height requirement) into Car 1, with one empty seat. Although the
attendant knew cars are supposed to be dispatched full, the next 30 or so patrons were all
members of the same football team, apparently university age, and wanted to sit together. In
addition, the attendant thought it did not seem appropriate to insist that the children ride with a
large male stranger. The attendant wanted to avoid making the wait worse. Upon further
questioning, the attendant indicated that he believed the no-empty-seat rule was about
throughput, and was unaware of a minimum weight requirement. The operator knew about the
need to avoid light cars, but did not evaluate the rider load or composition of the Car 1 because
the attendant loads the riders.
The operator on the control panel heard hollering from football players in Car 2 and their
teammates in the queue calling for attention. The operator located the reset controls quickly
because resetting is performed daily when the block braking system is tested. This test includes
stopping a car in a block and ensuring block brakes stop the following car, so the operator is
completely familiar with the function of the SRCS, but was focused on the noisy football team
and did not even notice the small, quiet middle-schoolers in Car 1.
Current ride design standards (ASTM F2291-18) require that the SRCS not allow an operator to
reset the system until verifying why the sensor was triggered, such as placing the reset near the
Car 2 collided with
Car 1 just before
Car 1 lacked
momentum to
reach and pass
dispatched Car 1
Operator manually
cleared Car 2 to
proceed from stop
at BZ2
SRCS stopped Car
2 at BZ2
Riders sustained
minor soft-tissue
Cars require mass
of X for adequate
Car 1 had mass
less than X
Natural low point
on track between
BZ2 and BZ3 for
light cars to stall
Car 1 stopped
short of BZ3
Each Brake Zone
has technology to
dispatch stopped
SRCS prevents
more than one Car
per block
Manually clearing
SRCS faults does
not require reset at
site of fault
Operator could not
see stopped car 1
from work position
location of the sensor. Physically going to this location to reset the sensor would have refreshed
the operator’s awareness of the stopped Car 1 and made the potential collision more apparent,
reminding the operator to remove Car 1 before restarting Car 2. However, this ride had not been
modified since the standard was revised, and therefore was subject to the standard as of its
manufacture. Designers generally have no training in human factors and do not operate rides,
therefore they may lack ability to foresee information overload in the operational environment,
and potential for the operator to overlook Car 1 when resetting the brake.
Using the notation of CSI:HF (course notes appendix), the Notes section about error typology,
and the information provided above, classify the type of error. If an error reflects two or more
contributing mechanisms, identify and classify each.
Use the following table and submit ONLY THE TABLE. If DropBox is provided, you may use
Acrobat typewriter to annotate on the pdf. Remove the two pages before uploading.
Alternatively, it is acceptable to neatly handwrite and scan as a pdf.
OHS 323 – Prof. K. Woodcock
Error worksheet
Student name Date
Error Person Mechanism Error

Sample Solution

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