The first roller coaster in the United States to loop upside down tucked riders by twos into bench seats, secured them with a single seat belt and subjected them to an estimated 7.5 times the force of gravity (some say it was closer to 12 g). The Flip Flap Railway opened in New York City’s Sea Lion Park in 1895, where the roller coaster reportedly strained backs, wrenched necks and dazzled spectators until the park closed in 1902.
Now, roller coaster safety is in the news again. In September, three lawsuits were filed against Six Flags and ride manufacturer S&S Global, alleging that riders sustained “catastrophic” brain injuries on the roller coaster X2 at California’s Magic Mountain theme park. These are just the most recent cases related to the ride, filed after a CNN investigation found dozens of injuries on X2 leading to hospitalization, disability and death. On September 29, Six Flags announced X2 would shut down permanently even though it said the ride “consistently passed a multitude of safety tests.”
Weeks later, the company said it would temporarily close another nine coasters across the United States and Canada after a man fell from his seat on the roller coaster Goliath and died at Six Flags Over Georgia. Six Flags announced Oct. 24 that it would add seat belts to Goliath and other coasters, and a spokesperson told Science News that the company is “committed to rigorous ride inspection, maintenance and safety procedures.” But the incidents and closures are prompting new questions about coaster design and safety — particularly when they are operating correctly — and whether guidelines overlook crucial factors.
“Taller, faster, longer”
Roller coasters are not regulated at the federal level in the United States; each state has its own approach to their management. But an international technical group comprising over 1,000 industry professionals, the ASTM Committee F24 on Amusement Rides and Devices, publishes recommendations that are considered industry standards.
The first ASTM standards for roller coaster design were released in 1982. The U.S. Consumer Product Safety Commission had been stripped of authority to regulate fixed-site amusement rides the year before. In the wake of this newfound freedom, it was a “roller coaster arms race,” says Brian Avery, an event and tourism management researcher at the University of Florida in Gainesville who studies risk and amusement ride safety protocols. The period was characterized by attempts to “build it taller, faster, longer.”
When X2, originally called X, opened in 2002, it was the world’s first fourth-dimension coaster. It catapulted people 60 meters high, traveling 122 kilometers per hour while its seats rotated independently on their own tracks. In the 24 years since, only 20 or so other fourth-dimension coasters have been built, and several have closed.
Beyond g-forces
As roller coasters grew more extreme, injuries increased and were more publicized, sparking calls for further research and regulation.
Generally, roller coasters are quite safe. Out of 1.7 billion annual amusement park rides across North America, just 652 roller coaster injuries were reported in 2024 by parks choosing to share data. Studies suggest that riding a roller coaster is very unlikely to cause a brain injury, although most research on roller coaster brain impacts is about a decade or more old.
In 2002, a study used reported g forces from three roller coasters in a mathematical model to determine that their acceleration levels were below those predicted to cause head injuries. A 2017 study found brain effects on three roller coasters that were low on average, but “comparable with mild sports impacts,” like those sustained by heading a soccer ball, at their peak.
“The limiting of g forces alone might be an insufficient design criterion for roller coaster rides,” wrote the authors of the 2017 study.
In 2020, David Eager, a biomechanical engineer at the University of Technology Sydney, coauthored a paper on under-acknowledged forces affecting roller coaster safety, including jerk (the rate at which acceleration changes), snap (the rate at which jerk changes) and vibration.
“Roller coaster passengers need time to sense acceleration changes and adjust their muscle tension or suffer conditions such as whiplash,” Eager wrote.
The ASTM standards are exacting in some ways. Research conducted during the space race led to a 6g recommended limit on roller coaster acceleration exposure. However, ASTM doesn’t make recommendations about other types of motion on a roller coaster that might impact the neck, head and brain. It disregards forces lasting less than 200 milliseconds, no matter how intense.
But each tiny imperfection and variation in the circumference of the track — especially plentiful in coasters built before modern manufacturing techniques — causes a jolt, says Jurnan Schilder, a mechanical engineer and researcher who teaches roller coaster design at the University of Twente in Amsterdam. He studies ways to create smoother roller coaster rides.
Schilder’s research suggests that at each track imperfection, “theoretically, you experience infinite jerk.” On a fourth-dimension coaster, he says, two sets of tracks mean double the variations. “Not only is the train sometimes shaking, but also the tilting mechanism is shaking.”
Impacting the brain
Research beyond rides also suggests intense and repeated rattling, jostling and vibration could meaningfully impact the brain. The U.S. Occupational Safety and Health Administration recommends limiting the duration and intensity of whole-body vibration. In April, the Virginia Tech Helmet Lab, which studies the science of brain injuries, published an article suggesting some concussions experienced by baseball players may result from just milliseconds of vibration.
North Carolina high school student Kayleigh Bonner’s quest to understand her father’s death exposed similar risks. After her father, a retired U.S. Coast Guard surfman who captained boats through rough waves for 21 years, experienced symptoms of a brain injury and died by suicide, Kayleigh surveyed 77 other elite surfmen for a senior capstone project. She found that 89 percent of those she spoke to had some symptoms of brain injury likely caused by the intense, rapidly changing forces traveling through their bodies as their boats were tossed by waves. Her quest to understand her father’s death was written about in July in the New York Times, and soon after acknowledged by the Coast Guard.
Of course, professional baseball players and Coast Guard surfmen have more significant and prolonged exposure to these forces than occasional roller coasters riders. But as researchers discover more about how different kinds of motion impact the brain, safety standards seem to lag behind. Minimizing jerk and snap is “an important consideration,” Eager says.
A push for greater regulation
The mounting roller coaster-related headlines have renewed scrutiny of both the existing coaster safety standards and the lack of federal regulation. U.S. Rep. André Carson, a Democrat from Indiana, has called to pass a bill he first introduced in 2025 that would create federal oversight of amusement rides. Since 1999, Democratic U.S. Sen. Ed Markey of Massachusetts has repeatedly introduced legislation to regulate fixed rides, but the bills have consistently stalled.
The amusement industry has long opposed federal oversight. In 2010, Avery coauthored a paper asserting that “the industry needs to find a collective voice and establish consistent self‐regulating policies in order to curb the incidents rates and avoid federal regulation.”
But Schilder says: “It makes you wonder: Are the current safety standards sufficient?”
For modern rides, Schilder says he believes they are. Modern manufacturing techniques mean roller coasters designed and built today are much smoother than predecessors. ASTM standards that filter out brief but intense forces, like vibration and jerk, are likely fine for rides that don’t vibrate and jerk very much. But at many parks, the ambitious and intense rides born of the roller coaster arms race are still in place.
Riders are “flirting, if you would, with danger when they experience rides and devices. They know that they’re more likely than not going to be safe,” Avery says. The point is to be “right on the cusp.”