Corkscrews, Cobra Rolls and Camel Backs
When was the last time you rode a roller coaster? Remember the rush of adrenaline as you crested a lift hill and started to accelerate downward? How it felt to be pulled toward the side of the car in the turns? How you screamed during "airtime"? (We'll explain that last one later.)
Perhaps you also remember a certain nervous feeling - let's call it "trepidation" (which sounds better than "scared out of your mind") - as you contemplated the swooping helix turns and double inversions you were about to launch yourself into.
The people who design and build coasters and other thrill rides understand the pleasure/fear paradox. They're constantly striving to come up with the tallest, the fastest, the twistiest, the scariest - but no matter how far they push the envelope, they know that the safety of their thrill-seeking audience is the most important part of their job.
That's where ASTM Committee F24 on Amusement Rides and Devices comes in. Formed in 1978, F24 is responsible for 19 standards relating to the design, performance, operation and maintenance of roller coasters, tower rides and even non-traditional attractions like parasailing and trampolines. Here's how this committee is keeping you safe this and every summer.
G-forces. Allowable acceleration. Reach envelope. These terms may conjure images of astronauts strapped into space capsules or pilots flying fighter jets, but they also relate to more earthbound - though no less gut-churning - forms of "transportation": roller coasters and other amusement park thrill rides.
One of the most valuable ways ASTM Committee F24 supports the industry is by facilitating development of testing protocols, performance specifications and maintenance procedures that manufacturers can use to ensure the safety of their rides. Take, for example, ASTM standard F2137, Practice for Measuring the Dynamic Characteristics of Amusement Rides and Devices.
Understanding the effect of g-forces (which are generated by steep drops and banked turns, known as the dynamic characteristics of a ride) on the human body and establishing a consensus regarding what's safe are obviously crucial aspects of any ride design. But first you need a universally accepted way to measure these forces as rides evolve from computer-aided drafting drawings on a computer screen to a finished attraction.
As vice president and chief safety officer for Walt Disney Parks and Resorts (and an ASTM Committee F24 member for more than 25 years), Greg Hale knows all about measuring g-forces, or g's.
"One of the more impactful standards that the committee developed to fill a critical need is F2137, which standardized how acceleration data is collected and electronically processed," Hale says. "Both the ASTM and EN [European Standards] committees were developing acceleration limits for amusement rides, but there was no consistent method for measuring and processing acceleration data. Depending on the sampling rates and filtering used, you could get measurements on the same ride of 2 g's or 20 g's. Additional information related to human reactions to acceleration enabled the committee to publish ASTM F2137, a standard that's accepted worldwide and delivers reliable and repeatable g-force data."
Internationally accepted standards are especially important to the theme and amusement park industry, which is itself a truly global phenomenon. For example, ride developers and manufacturers hail from all corners of the globe\; well-known theme park brands founded in North America continue to expand their reach into Asia, Europe and India.
In such a diverse environment - where, for example, smaller average body sizes in Asia might require modified restraint designs, cultural trends must be considered (such as "selfie sticks") and every ride manufacturer is pushing the envelope to come up with the next big thing - a central clearinghouse for standards development is crucial.
Katerina Koperna is the ASTM staff manager of Committee F24. She emphasizes the importance of the committee's international membership and the role it plays in addressing new issues - such as the aforementioned selfie sticks. According to Koperna, the exploding popularity of these gizmos (which, as you can imagine, are extremely dangerous on a moving ride) could lead F24 to develop revised standards for restricted items on rides as well as signage to help park operators around the world deal with the problem.
As chief operating officer at Vekoma, a major ride manufacturer based in the Netherlands, Har Kupers is quite familiar with the many steps involved in creating a new attraction and the value of solid, science-based standards.
"We start with the design of the layout of the ride, at which point we must take g-forces into account," says Kupers, an F24 member since 2000. "These vary depending on the type of ride - for example, a family coaster with limited g-forces or a thrill ride with inversion elements and higher g-forces. Committee F24 provides good limits for g-force levels."
Once engineers determine that a ride's g-force levels are safe, attention turns to the structural design of the track, supporting structures and the vehicle in which people will experience the ride. Kupers points out that ride elements like vehicle restraint configurations, track-side equipment and control systems also fall under the purview of Committee F24 and cites the value to companies like Vekoma of both the standards the committee has helped develop and its efforts to reconcile differences between these standards and others already in place around the world.
Disney's Greg Hale has led F24's international standards harmonization efforts for a number of years. As an example of the benefits of this activity, he points to the United States' neighbor to the north.
"I would say that our efforts with Canada have been one of the biggest harmonization success stories," Hale says. "The Canadian Standards Authority actually started an amusement ride standards committee 37 years ago and issued standard Z-267 before the ASTM F24 committee was established. After years of maintaining that standard to try and stay consistent with ASTM F24, they approached ASTM to develop a standard for Canada that would embody the F24 standards and allow them to focus on participation in ASTM F24 instead of trying to maintain their own standard. This effort wrapped up last year with the publication of ASTM F2783 for amusement rides in Canada, and they have officially retired their committee and Z-267 standard."
Matthias Rohde, D.Ing, a professor at Germany's Frankfurt University of the Applied Sciences, is an F24 member with a unique history in the industry. His father was an amusement park ride inspector and "after they were accepted, I was often the first one to ride them."
Rohde was also a key participant in harmonization of F24 standards with EN 13814, the European amusement ride safety standard. He believes ASTM's status as a not-for-profit, nongovernmental organization that operates across borders, with a focus on "safety and reducing misunderstandings between designers, manufacturers and customers," is key to its success in achieving consensus.
One of the most interesting challenges of designing a crowd-pleasing amusement park attraction is understanding the relationship between ride and riders. While, say, a suspension bridge may share key components like concrete, rebar and structural steel with a roller coaster, bridge designers don't have to focus much on Kathryn Woodcock's area of expertise: human factors engineering, which, in her words, "looks at how the interaction of people and technology affects the performance of the whole system."
Woodcock, Ph.D., P.E., is a professor at Ryerson University in Toronto, Ontario, Canada, and director of the school's THRILL (Tools for Holistic Ride Inspection Learning and Leadership) program. A key focus area for the program's research is helping to create rides that account for the wide range of individual capabilities and limitations. Woodcock points out that, "In any setting, ‘accessibility issues' are simply design conventions that don't work for certain people. Some attractions are inherently accessible or can be intentionally designed with inclusive design principles at the outset. Alternatively, existing designs sometimes can subsequently be modified to remove barriers.
"For example, we have seen multiple sizes of ride seats for guests who are large or small, seats that allow guests to transfer from wheelchairs or even remain in the wheelchair while on the ride, supplementary restraint devices to contain guests who have amputations, and subtitles and audio description of video material in the pre-attraction briefing and the show itself for guests who are deaf or blind," Woodcock says. "The ASTM F24 standards consider that some guests may participate with a supervising companion, enabling them to ride when they might not be able to safely experience the ride alone due to age or disability."
Kathryn Woodcock makes an interesting point about the whole phenomenon of thrill rides. "The attractions industry doesn't manufacture conventional products or other tangibles. It is a system that produces fun, and not only do people vary in their individual capabilities and limitations, but they also vary in their goals and definitions of fun," she says.
Whatever your definition of fun is, whether you're enjoying airtime - that's when your body lifts out of the seat due to negative g-forces, usually on a drop or at the crest of a hill - or dangling under the track on a suspended roller coaster, you can rest assured that hundreds of experts spanning the universe of amusement park stakeholders are working through ASTM Committee F24 to ensure your safety.
Jack Maxell is a freelance writer based in Westmont, New Jersey. While putting this article together, he took virtual rides on some of the world's biggest coasters and only screamed once.