Roller Coaster - Safety

Safety

Many safety systems are implemented in roller coasters. One of these is the block system. Most large roller coasters have the ability to run two or more trains at once, and the block system prevents these trains from colliding. In this system, the track is divided into several sections, or blocks. Only one train at a time is permitted in each block. At the end of each block, there is a section of track where a train can be stopped if necessary (either by preventing dispatch from the station, closing brakes, or stopping a lift). Sensors at the end of each block detect when a train passes so that the computer running the ride is aware of which blocks are occupied. When the computer detects a train about to travel into an already occupied block, it uses whatever method is available to keep it from entering. The trains are fully automated.

The above can cause a cascade effect when multiple trains become stopped at the end of each block. In order to prevent this problem, ride operators follow set procedures regarding when to release a newly loaded train from the station. One common pattern, used on rides with two trains, is to do the following: hold train #1 (which has just finished the ride) right outside the station, release train #2 (which has loaded while #1 was running), and then allow #1 into the station to unload safely.

Another key to safety is the control of the roller coaster's operating computers: programmable logic controllers (often called PLCs). A PLC detects faults associated with the mechanism and makes decisions to operate roller coaster elements (e.g. lift, track-switches and brakes) based on configured state and operator actions. Periodic maintenance and inspection are required to verify structures and materials are within expected wear tolerances and are in sound working order. Sound operating procedures are also a key to safety.

Roller coaster design requires a working knowledge of basic physics to avoid uncomfortable, even potentially fatal, strain to the rider. Ride designers must carefully ensure the accelerations experienced throughout the ride do not subject the human body to more than it can handle. The human body needs time to detect changes in force in order to control muscle tension. Failure to take this into account can result in severe injuries such as whiplash. The accelerations accepted in roller coaster design are generally in the 4-6Gs (40–60 m s−2) range for positive vertical (pushing you into your seat), and 1.5-2Gs (15–20 m s−2) for the negative vertical (flying out of your seat as you crest a hill). This range safely ensures the majority of the population experiences no harmful side effects. Lateral accelerations are generally kept to a minimum by banking curves. The neck's inability to deal with high forces leads to lateral accelerations generally limited to under 1.8Gs. Sudden accelerations in the lateral plane result in a rough ride.

Despite safety measures, accidents can, and do, occur. Regulations concerning accident reporting vary from one authority to another. Thus in the USA, California requires amusement parks to report any ride-related accident that requires an emergency room visit, while Florida exempts parks whose parent companies employ more than 1000 people from having to report any accidents at all. Rep. Ed Markey of Massachusetts has introduced legislation that would give oversight of rides to the Consumer Product Safety Commission (CPSC).

Ride accidents can also be caused by riders themselves or ride operators not following safety directions properly, and, in extremely rare cases, riders can be injured by mechanical failures. In recent years, controversy has arisen about the safety of increasingly extreme rides. There have been suggestions that these may be subjecting passengers to translational and rotational accelerations that may be capable of causing brain injuries. In 2003 the Brain Injury Association of America concluded in a report that "There is evidence that roller coaster rides pose a health risk to some people some of the time. Equally evident is that the overwhelming majority of riders will suffer no ill effects."

A similar report in 2005 linked roller coasters and other thrill rides with potentially triggering abnormal heart conditions that could lead to death. Autopsies have shown that recent deaths at various Disney parks, Anheuser-Busch parks, and Six Flags parks were due to previously undetected heart ailments.

Statistically, roller coasters are very safe compared to other activities. The U.S. Consumer Product Safety Commission estimates that 134 park guests required hospitalization in 2001 and that fatalities related to amusement rides average two per year. According to a study commissioned by Six Flags, 319 million people visited parks in 2001. The study concluded that a visitor has a one in one-and-a-half billion chance of being fatally injured, and that the injury rates for children's wagons, golf, and folding lawn chairs are higher than for amusement rides.