Rollercoaster Crash Under Investigation

By ThinkReliability Staff

A day at a resort/ theme park ended in horror on June 2, 2015 when a carriage filled with passengers on the Smiler rollercoaster crashed into an empty car in front of it. The 16 people in the carriage were injured, 5 seriously (including limb amputations). While the incident is still under investigation by the Health and Safety Executive (HSE), information that is known can be collected in cause-and-effect relationships within a Cause Map, or visual root cause analysis.

The analysis begins with determining the impact to the goals. Clearly the most important goal affected in this case is the safety goal, impacted because of the 16 injuries. In addition to the safety impacts, customer service was impacted because of the passengers who were stranded for hours in the air at a 45 degree angle. The HSE investigation and expected lawsuits are an impact to the regulatory goal. The park was closed completely for 6 days, at an estimated cost of ?3 M. (The involved rollercoaster and others with similar safety concerns remain closed.) The damage to the rollercoaster and the response, rescue and investigation are impacts to the property and labor goals, respectively.

The Cause Map is built by laying out the cause-and-effect relationships starting with one of the impacted goals. In this case, the safety goal was impacted because of the 16 injuries. 16 passengers were injured due to the force on the carriage in which they were riding. The force was due to the speed of the carriage (estimated at 50 mph) when it collided with an empty carriage. According to a former park employee, the collision resulted from both a procedural and mechanical failure.

The passenger-filled carriage should not have been released while an empty car was still on the tracks, making a test run. It’s unclear what specifically went wrong to allow the release, but that information will surely be addressed in the HSE investigation and procedural improvements going forward. There is also believed to have been a mechanical failure. The former park employee stated, “Technically, it should be absolutely impossible for two cars to enter the same block, which is down to sensors run by a computer.” If this is correct, then it is clear that there was a failure with the sensors that allowed the cars to collide. This will also be a part of the investigation and potential improvements.

After the cause-and-effect relationships have been developed as far as possible (in this case, there is much information still to be added as the investigation continues), it’s important to ensure that all the impacted goals are included on the Cause Map. In this case, the passengers were stranded in the air because the carriage was stuck on the track due to the force upon it (as described above) and also due to the time required for rescue. According to data that has so far been released, it was 38 minutes before paramedics arrived on-scene, and even longer for fire crews to arrive with the necessary equipment to begin a rescue made very difficult by the design of the rollercoaster (the world record holder for most loops: 14). The park staff did not contact outside emergency services until 16 minutes after the accident – an inexcusably long time given the gravity of the incident. The delayed emergency response will surely be another area addressed by the investigation and continuing improvements.

Although the investigation is ongoing, the owners of the park are already making improvements, not only to the Smiler but to all its rollercoasters. In a statement released June 5, the owner group said “Today we are enhancing our safety standards by issuing an additional set of safety protocols and procedures that will reinforce the safe operation of our multi-car rollercoasters. These are effective immediately.” The Smiler and similar rollercoasters remain closed while these corrective actions are implemented.

Dr. Tony Cox, a former Health and Safety Executive (HSE) advisory committee chairman, hopes the improvements don’t stop there and issues a call to action for all rollercoaster operators. “If you haven’t had the accident yourself, you want all that information and you’re going to make sure you’ve dealt with it . . . They can just call HSE and say, ‘Is there anything we need to know?’ and HSE will . . . make sure the whole industry knows. That’s part of their role. It’s unthinkable that they wouldn’t do that.”

To view the information available thus far in a Cause Map, please click “Download PDF” above.