PROJECT REPORT Human Factors Review of Restraint Failures on Mobile Amusement Rides February 2005 Timothy P. Smith, Project Manager Division of Human Factors Directorate for Engineering Sciences U.S. Consumer Product Safety Commission Washington, DC 20207 301-504-7691, [email protected] This report has not been reviewed or approved by, and may not reflect the views of, the Commission. Contents Executive Summary................................................................................................................II Introduction............................................................................................................................1 Annual Injuries and Deaths..................................................................................................3 Market and Product Information.........................................................................................4 Amusement Ride Standards..................................................................................................5 Hazard Patterns.......................................................................................................................8 Restraint Failure Data Sources.......................................................................................9 Restraint Failure Hazard Patterns................................................................................10 Restraint Unexpectedly Opens...........................................................................................13 Component Failures......................................................................................................13 Non-component Failures.............................................................................................14 Potential Preventive Measures.....................................................................................14 Rider Defeats Restraint........................................................................................................16 Restraint Design.............................................................................................................16 Cognitive Development................................................................................................17 Thrill-Seeking Behavior................................................................................................18 Other Possible Factors..................................................................................................19 Potential Preventive Measures.....................................................................................19 Conclusions...........................................................................................................................21 References..............................................................................................................................22 Appendix A: Sample Restraint Images..............................................................................24 Appendix B: Relevant CPSC Investigations.....................................................................26 Appendix C: Relevant State Investigations.......................................................................30 HF REVIEW OF RESTRAINT FAILURES ON MOBILE AMUSEMENT RIDES I Executive Summary In fiscal year 2004, staff from the U.S. Consumer Product Safety Commission Division of Human Factors initiated a project to examine restraint failures associated with mobile amusement rides. The staff reviewed available incident data associated with apparent restraint failures on mobile amusement rides, identified scenarios associated with restraint-failure incidents, and identified contributing factors to those failures or incidents. An estimated 2,800 to 4,300 non-occupational emergency-room-treated injuries were associated with mobile amusement rides for each year from 1997 through 2003. The proportion associated with restraint failures is unknown. Ten to seventeen documented deaths for the years 1987 to 2001, or no more than about one death every year, involved a mobile amusement ride. The number associated with restraint failures is unknown, but is likely to be considerably smaller. The available incident data suggests that most restraint-failure incidents involve either the restraint system unexpectedly opening during the ride cycle or the rider deliberately defeating the restraint system. Restraint or latch designs that allow operators to readily identify the status of the restraint as either open or closed may address some incidents associated with the restraints unexpectedly opening. The most effective preventive measure, however, would be to require redundant or secondary restraints on all rides from which a rider could be thrown if the primary restraint unexpectedly opened. This would likely be effective at preventing all incidents associated with this scenario, whether due to a component failure or not. Preventing incidents associated with riders defeating restraint systems would be considerably more difficult, and would require making the rides essentially rider- proof. Many of these incidents seem to involve very young riders, who have limited cognitive development and are unlikely to recognize the consequences of their actions. Specific recommendations for injury prevention would require more detailed analyses of rides, restraints, and the particular methods employed by riders to escape. Secondary restraints may slow riders’ escape and provide the operator with more time to stop the ride, and reducing the time for a ride to stop would limit the time available to a rider to escape after being detected. It is unclear, however, how effective these measures would have been at preventing the incidents on record. HF REVIEW OF RESTRAINT FAILURES ON MOBILE AMUSEMENT RIDES II Introduction Reports of riders falling or being thrown from amusement rides have prompted the staff of the U.S. Consumer Product Safety Commission (CPSC) to examine the adequacy of ride-restraint systems. Specifically, staff from the CPSC Division of Human Factors (“the staff”) initiated a project in fiscal year 2004 to examine apparent restraint failures on mobile amusement rides. Restraint failures on amusement rides may be particularly hazardous because the rides often involve high speeds and sudden changes in direction. The primary objectives of this project were to determine whether the restraint systems on mobile amusement rides are sufficient to protect riders, and if necessary, to determine what steps could be taken to improve the safety of deficient systems. To make these determinations, the staff reviewed incident data associated with restraint failures on mobile amusement rides, identified primary hazard patterns or scenarios associated with those incidents, and identified possible factors that contributed to the failures or incidents. An amusement ride is any device, or combination of devices or elements, that carries, conveys, or directs one or more people along, around, over, or through a fixed or restricted route or within a defined area, primarily for amusement or entertainment.1 As specified in Section 3(a)(1) of the Consumer Product Safety Act (15 U.S.C. § 2052(a)(1)), the CPSC currently has jurisdiction over mobile, or portable, amusement rides; that is, amusement rides that can be moved as part of carnivals, fairs, festivals, or other events. Fixed-site rides, which are commonly found in amusement parks, theme parks, or similar locations, are not under CPSC jurisdiction. What constitutes a restraint failure may be open to interpretation. Amusement-ride restraints are intended to inhibit or restrict the movement of the rider while on the amusement ride.2 From this, one might infer that a restraint has failed any time the rider’s movements are not restricted or inhibited. Complete immobilization of the rider, however, is clearly not feasible, so some degree of movement is permissible. Any incident in which the rider falls or is thrown from the ride would seem relevant, yet incidents involving the rider being thrown from his or her seat while remaining on the ride would also seem relevant. Some rides require the rider to be prone on the ride, and would therefore lack seats. Also, a ride that lacks a restraint and allows a rider to be thrown could be considered relevant since the ride has failed, by omission, to restrain the rider. Hence, the staff considers a restraint failure to have occurred any time the rider leaves the intended riding position during the ride cycle. For example, a restraint has not failed simply because a rider lets go of a safety bar, even if the manufacturer of that ride intends for the rider to hold the bar for the 1 Based on the definition of “amusement ride or amusement device” in ASTM F 747 – 97, Standard Terminology Relating to Amusement Rides and Devices, and on the description of products under the jurisdiction of the CPSC specified in Section 3(a)(1) of the Consumer Product Safety Act (15 U.S.C. § 2052(a)(1)). 2 Based on the definition of “restraint” in ASTM F 2291 – 04, Standard Practice for Design of Amusement Rides and Devices. HF REVIEW OF RESTRAINT FAILURES ON MOBILE AMUSEMENT RIDES 1 entire ride cycle. If, however, the rider leaves the seat or other riding position after letting go of that safety bar, the staff considers a restraint failure to have occurred. All incidents consistent with the above are considered to be within the scope of this project. The types of amusement rides addressed in this study include all “dry” mobile amusement rides (i.e., water slides and similar amusements are excluded) except inflatable rides, coin-operated rides or attractions that are typically found in restaurants and shopping centers, alpine slides,3 mechanical bulls, and playground equipment. Rider-directed amusement rides, such as go-carts and bumper cars, are also considered outside the scope of this project. 3 An alpine slide is a slide or chute that is constructed on, and follows the natural contours of, the ground HF REVIEW OF RESTRAINT FAILURES ON MOBILE AMUSEMENT RIDES 2 Annual Injuries and Deaths Based on National Electronic Injury Surveillance System (NEISS) estimates, about 2,800 to 4,300 non-occupational emergency-room-treated injuries were associated with mobile amusement rides for each year from 1997 through 2003 (Levenson, 2004). Most injuries were to people between 5 and 44 years of age, and females were injured more often than males (Levenson, 2002). The limited detail available in the NEISS data do not enable staff from the CPSC Directorate for Epidemiology to provide annual estimates of injuries associated with restraint failures on mobile amusement rides. The available data, however, suggests that injuries associated with restraint failures may represent a relatively small percentage of the total annual estimates.4 The CPSC has received reports of 55 deaths associated with both fixed-site and mobile amusement rides from 1987 to 2001; 10 involved mobile rides and seven involved rides for which the site could not be identified (Levenson, 2004). These counts suggest that the number of mobile-amusement-ride-related deaths each year is, on average, likely to be less than one. The number associated with restraint failures is unknown, but is likely to be considerably smaller. For 2002 through 2004, the CPSC has received reports of nine additional deaths associated with amusement rides, but reporting for these years is incomplete (Levenson, 2004). One of these reports involved a ride for which the site could not be identified, and may therefore have involved a mobile ride. 4 See Hazard Patterns: Restraint Failure Data Sources on page 9 of this report. HF REVIEW OF RESTRAINT FAILURES ON MOBILE AMUSEMENT RIDES 3 Market and Product Information According to the Outdoor Amusement Business Association (OABA) (2004a), about 500 carnivals travel the U.S. each year, ranging in size from one or two mobile rides to more than a hundred. About 300 to 500 million people visit carnivals, fairs, and festivals each year,5 and more than half of these people participate on mobile amusement rides (OABA, 2004c). Amusement rides, including mobile ones, vary widely in design, and there is limited agreement among manufacturers on general ride categories or types. However, amusement rides within the scope of this project can generally be separated into roller coasters and flat rides. According to ASTM F 747 – 97, Standard Terminology Relating to Amusement Rides and Devices, a flat ride is “an amusement ride that operates on a single level whether over a controlled, fixed course or track, or confined to a limited area of operation.” More common use of the term seems to include any dry, non-rider-operated amusement ride other than roller coasters, including whirling or spinning rides, swinging rides, trains, pendulum rides, and similar rides. However, as mentioned earlier, these particular ride descriptors are not used consistently. There appears to be no readily available information on the specific restraint systems used on mobile amusement rides. Staff from the CPSC Directorate for Economic Analysis was unable to locate information on the types of restraint systems in use on rides, or on general restraint designs. When describing the restraints in use, the available incident data4 refer primarily to lap bars and seatbelts, and less often to chains, crotch straps, ropes, shoulder harnesses, body harnesses, and security cages. These data typically provide very little detail about these restraint systems beyond this general description. Some data include photos of the restraints, and sample images appear in Appendix A. 5 Three separate estimates appear on the Outdoor Amusement Business Association’s website: 300 million (OABA, 2004a), 350 million (OABA, 2004b), and 500 million (OABA, 2004c). HF REVIEW OF RESTRAINT FAILURES ON MOBILE AMUSEMENT RIDES 4 Amusement Ride Standards There are no mandatory federal standards for amusement rides. ASTM International6 publishes the only nationally recognized U.S. voluntary standards for amusement rides. The ASTM Committee F24 on Amusement Rides and Devices currently has jurisdiction of 15 active standards that cover test methods, specifications and terminology, design and manufacture, maintenance and inspection, and operations for amusement rides and devices. The following table lists these standards: Designation Title Test Methods F 846 – 92(2003) Standard Guide for Testing Performance of Amusement Rides and Devices F 1957 – 99 (2004) Standard Test Method for Composite Foam Hardness- Durometer Hardness F 2137 – 04 Standard Practice for Measuring the Dynamic Characteristics of Amusement Rides and Devices Specifications F 698 – 94(2000) Standard Specification for Physical Information to be and Provided for Amusement Rides and Devices Terminology F 747 – 97 Standard Terminology Relating to Amusement Rides and Devices F 1950 – 99 Standard Specification for Physical Information to be Transferred With Used Amusement Rides and Devices Design and F 1159 – 03a Standard Practice for Design and Manufacture of Patron Manufacture Directed, Artificial Climbing Walls, Dry Slide, Coin Operated and Purposeful Water Immersion Amusement Rides and Devices and Air-Supported Structures F 1193 – 04b Standard Practice for Amusement Ride and Device Manufacturer Quality Assurance Program and Manufacturing Requirements F 2291 – 04a Standard Practice for Design of Amusement Rides and Devices Maintenance F 853 – 04 Standard Practice for Maintenance Procedures for and Inspection Amusement Rides and Devices F 893 – 04 Standard Guide for Inspection of Amusement Rides and Devices 6 Formerly known as the American Society for Testing and Materials. HF REVIEW OF RESTRAINT FAILURES ON MOBILE AMUSEMENT RIDES 5 Designation Title Operations F 770 – 93(2000) Standard Practice for Operation Procedures for Amusement Rides and Devices F 1305 – 94(2002) Standard Guide for Classification of Amusement Ride and Device Related Injuries and Illnesses Special Rides/ F 2007 – 00 Standard Practice for the Classification, Design, Attractions Manufacture, and Operation of Concession Go-Carts and Facilities F 2374 – 04 Standard Practice for Design, Manufacture, Operation, and Maintenance of Inflatable Amusement Devices These standards do not distinguish between fixed-site and mobile amusement rides, and thus apply to both types of rides. Of these standards, only ASTM F 2291, Standard Practice for Design of Amusement Rides and Devices, specifies rider restraint requirements. The specific requirements for a given ride or device are dependent on the results of a Ride Analysis, which is specified in Section 5.1 of ASTM F 2291 – 04 and includes a Patron Restraint and Containment Analysis, a Patron Clearance Envelope Analysis, and Failure Analyses on the safety related systems of the ride or device. The Ride Analysis must assess the suitability of design for the intended patrons, including anthropomorphic factors that relate to age and physical size, and must both identify the most significant factors that may affect patron safety and include mitigation for each factor. The standard does not define “most significant,” and does not identify mitigation that would be considered appropriate. The Patron Restraint and Containment Analysis (PRCA) must be done in accordance with Section 6 of the standard, which specifies patron restraint, clearance envelope, and containment design criteria. Unless the PRCA indicates otherwise, restraints must be provided on an amusement ride if it is reasonably foreseeable that riders could be lifted or ejected from their riding positions during the ride cycle, or if the ride is a “kiddie” ride that lacks a fully enclosed compartment.7 However, the PRCA may indicate the need for restraints for other reasons. The standard identifies five different classes of restraints that may be required on an amusement ride. The restraint class that is required on a specific ride is based, in part, on the sustained acceleration levels of the ride. Those rides that exhibit greater accelerations in directions that tend to lift or eject a rider generally require a higher class of restraint. For example, for two rides with similar sustained horizontal 7 “Kiddie” rides are rides designed primarily for children up to 12 years of age. A “fully enclosed compartment” is defined as a compartment whose openings will not permit passage of a 4-inch diameter sphere (Section 6.3.3). HF REVIEW OF RESTRAINT FAILURES ON MOBILE AMUSEMENT RIDES 6 accelerations, a ride that accelerates downward and would tend to cause the rider to rise in his or her seat would generally require a higher-class restraint than a ride that does not accelerate downward. Class-1 restraints are defined as unrestrained, but restraint criteria are specified for each of the remaining four classes of restraints (Class 2 through Class 5). These criteria are shown in the following chart:8 Class 2 Class 3 Class 4 Class 5 Number of riders per restraint Individual or collective........................................................ • • Individual.............................................................................. • • Final latching position relative to rider Fixed or variable................................................................... • Variable.................................................................................. • • • Type of latching/locking Rider or operator may latch................................................ • • Automatic lock..................................................................... • • Type of unlatching/unlocking Rider or operator may unlatch........................................... • • Automatic or manual unlock by operator only................ • • Type of external correct/incorrect indication None required....................................................................... • Visual check by operator..................................................... • • Primary system failure detectable within one ride cycle.. • External indication required............................................... • Failure causes cycle stop or inhibits cycle start................ • Means of activation Manually or automatically opened and closed.................. • • • • Redundancy or latching/locking device Redundancy not required.................................................... • • Redundant locking device function................................... • • Restraint configuration Two restraints or one fail-safe restraint............................ • To provide some perspective, the sustained acceleration levels of a person sitting upright and motionless in a chair would correspond to a Class-2 restraint. 9 8 Based on Table X1.1 in ASTM F 2291 – 04. Kiddie rides may have additional requirements beyond those identified in this chart. The characteristics identified for Class-5 restraints are for primary restraints only. Secondary restraints have less stringent requirements. 9 This would correspond to 0.0g horizontally and 1.0g vertically. As confirmed in correspondence with an industry representative, accelerations of this type would require a Class-2 restraint unless riders are provided sufficient support and a way to react to the forces. HF REVIEW OF RESTRAINT FAILURES ON MOBILE AMUSEMENT RIDES 7