Observed Human Error

Human Error Observed in Operation and Use of Carnival Rides
- Riders, Guardians, and Operators

From "Rider Responsibility and Amusement Ride Accidents: An Observational and Consensus Study of Rider Behaviours", Woodcock and Tsao, Proceedings of the Human Factors and Ergonomics Society 49th Annual Meeting (2005).

The three carnivals observed in the study had 103 separate installations of 88 different rides and attractions. In total, over 5000 rider exposures were observed. Observers took note of the safety rules posted on or around the ride, then stationed themselves unobtrusively near the rides and observed for several ride cycles, noting safety-related errors including violations of posted rules. Errors were classified according to who initiated the error (operator, rider, or parent/observer), and by type of error (lapse, violation, mistake, slip). [return to editorial]

Rider	Lapse	Violation	Mistake	Slip
Hanging/leaning out of seat, turning in seat		11
Horseplay, queue jumping		2	2
Extending arms/legs out of ride, not hanging on		3
Seated improperly		3
Slide (dry slide device) other than prescribed feet first position		3
Improperly restrained		2
Enter, exit via improper, unsafe route			5
Rushing start			4
Touch/attempt to touch hazardous parts			3
Chewing gum, food			2
Preparing to exit when mistaking pause for conclusion			2
Rider oversize or undersize for the restraint			2
Rocking, swinging the seat			2
Too many riders in the seat			1
Leave personal affects in traffic path			1
Rushing to alight before ride is over			1	5
Tripping while entering, exiting or in the ride				6
Rider subtotal		26	23	11

Guardian	Lapse	Violation	Mistake	Slip
Adult (e.g., parent) grasps/high-fives child on ride			2
Guardian subtotal			2

Operator	Lapse	Violation	Mistake	Slip
Restraint not checked	4
Defect not corrected (ride condition or loading)	3
Operator absent, not watching, or dozing	1	2
Direct riders to extend arms, not hang on		2
Encourage oversize or undersize rider		1
Use unsafe route or direct riders to do so			2
Entering moving machinery (self or rider)			2
Overload seat			1
Starting before rider in position				1
Operator subtotal	8	5	5	1

TOTAL	Lapse	Violation	Mistake	Slip
Errors per 5000 rider exposures = 81	8	31	30	12

Note 1:	Only 6 minor injuries were observed, none requiring any treatment at the time. The observed rider error rate was approximately 1.4% of the ride exposures observed in comparison to the observed injury rate of 0.1%.
Note 2:	Errors were classified using Reason's taxonomy (see Human Error, James Reason, 1990):
	Slips - Execution errors with no particular inappropriate intent (e.g., inaccurate execution of an intended action, misordering, mistiming, or attentional failure)
	Lapses - Omission of a required act (e.g., omitting planned items, losing place in a sequence of steps, or forgetting)
	Mistakes - Errors of judgment (e.g., making an inappropriate choice because of lack of information or knowledge, misinterpreting the situation, misapplication of good rule, or application of bad rules)
	Violations - Knowingly violating a rule as an exception or routine; sometimes motivated by intent to improve the outcome (e.g., riding with hands in the air to get a bigger thrill) and sometimes to defeat the outcome (e.g., sabotage)