Question: How many steel roller coasters of the same type as The Swarm are currently operating worldwide?

full_context: Document 1: WindSeeker: WindSeeker (known as SteelHawk at Worlds of Fun) is a 301 ft swing ride at several Cedar Fair parks. The rides are Wind Seeker models manufactured by Mondial. They opened for the 2011 season at Canada's Wonderland in Ontario, Cedar Point and Kings Island in Ohio, and Knott's Berry Farm in California. Carowinds in North Carolina and Kings Dominion in Virginia opened their WindSeekers in 2012. The first four each cost US$5,000,000, and the next two each cost $6,500,000. Cedar Fair relocated the Knott's Berry Farm WindSeeker to Worlds of Fun in 2014, where it is known as SteelHawk.
Document 2: Wing Coaster: A Wing Coaster is a type of steel roller coaster manufactured by Bolliger & Mabillard where pairs of riders sit on either side of a roller coaster track in which nothing is above or below the riders. Development of the Wing Coaster began between 2007 and 2008 leading to the opening of Raptor at Gardaland, the world's first Wing Coaster, on 1 April 2011. There are currently eight Wing Coasters operating worldwide.
Document 3: The Swarm (roller coaster): The Swarm is a steel Wing Coaster at Thorpe Park, a theme park in the United Kingdom. "The Swarm" was the world's second Wing Coaster designed by Swiss roller coaster manufacturer Bolliger & Mabillard and the United Kingdom's first Wing Coaster. Construction commenced in May 2011, and the coaster opened on 15 March 2012. Starting in 2013, the last two rows of each train face backwards, while the first five rows face forward. This was removed in 2016, with all riders facing forward once again.
Document 4: Superman: Ultimate Flight: Superman: Ultimate Flight is a steel flying roller coaster designed by Bolliger & Mabillard. Themed to the popular comic book character, "Superman: Ultimate Flight" has been installed at three Six Flags theme parks around the United States: Six Flags Over Georgia, Six Flags Great Adventure and Six Flags Great America. "Superman: Ultimate Flight" simulates flying by positioning its passengers parallel to the track, supported by harnesses and facing the ground through most of the ride. In the station, riders board the train sitting down. After the train is locked and checked, the trains are raised into the flying position. After the ride, the seats are lowered back into the sitting position for the next round of riders.
Document 5: Skycoaster: Skycoaster is an amusement park ride, produced and managed by Skycoaster, Inc., owned division of Ride Entertainment Group. On the ride, riders in groups of 1 to 3 are winched to the top of a launch tower and then dropped towards the ground, swinging from a cable tether back and forth until brought to a rest. Sky Coasters can range from 100 - in height. Skycoaster is an upcharge attraction at most installations, an additional fare is charged to riders who have already paid general admission to the park, and so must pay again for each ride. Names for the ride include variations of Skycoaster, along with Dare Devil Dive (at Six Flags parks), RipCord, and Xtreme Skyflyer (at Cedar Fair parks).
Document 6: Steel roller coaster: A steel roller coaster is a roller coaster that is defined by having a track made of steel. Steel coasters have earned immense popularity in the past 50 years throughout the world. Incorporating tubular steel track and polyurethane-coated wheels, the steel roller coasters can provide a taller, smoother, and faster ride with more inversions than a traditional wooden roller coaster.
Document 7: Behemoth (roller coaster): Behemoth is a steel roller coaster at Canada's Wonderland in Vaughan, Ontario, Canada. It is a Hypercoaster designed and developed by Swiss manufacturer, Bolliger & Mabillard. Behemoth was the tallest and fastest roller coaster in Canada until 2012 when Leviathan, a roller coaster also manufactured by Bolliger & Mabillard, was built at the opposite side of Canada's Wonderland, claiming these titles. Behemoth is similar to Diamondback (Kings Island), Goliath (La Ronde) and Nitro (Six Flags Great Adventure).
Document 8: Submission (Alton Towers): Submission was a Chance Rides Double Swinging Inverter located in the X-Sector area and was built in 2001. From 2005, the ride only operated one of its arms to save electricity and the ride's cycles were shortened. The slogan used in advertisement was 'Hang in there'. Following the area's theme, the ride was painted blue and was covered in a shiny metal, most likely steel. Each of its two arms had a counterweight in the shape of two metal spikes, which would sweep near to the ground like a scythe. The sequence was always the same, different to some other weight based rides that have numerous sequences, this was also probably to be more energy efficient. The Ride type itself is a rare flat-ride and not seen at a lot of themeparks, Submission did not have the best of reviews at Alton Towers mainly due to it having the same sequence (unlike others such as Ripsaw), the restraints were very similar to those on a Huss Top Spinner making it fairly uncomfortable to ride when inverted, breakdowns occasionally happened and as a result, queues were very short. In 2013 it was later revealed that Submission would be closed after the end of the 2013 season by which there is a vacant grass area where it once stood next to the break-block section on Oblivion. The grass area is often referred to as the 'Submission memorial ground' by thrill-seekers which has become a popular sitting area in the park section.
Document 9: Raptor (Cedar Point): Raptor is a steel inverted roller coaster designed by Bolliger & Mabillard at Cedar Point in Sandusky, Ohio, United States. When built in 1994, it broke many records and held many firsts when it opened. Instead of having a short layout designed to fit into a compact area like , Raptor was designed with a larger, 3,790-foot (1,160 m) layout, making it the tallest, fastest and longest inverted roller coaster in the world when it opened. It features six inversions, including a cobra roll, a first for inverted roller coasters. At its opening, it was the largest investment in Cedar Point history. The ride is themed as a bird of prey.
Document 10: Colossus (Thorpe Park): Colossus is a roller coaster at Thorpe Park in Surrey, England, and the park's first major attraction. It was built by Swiss manufacturers Intamin and designed by Werner Stengel as an adaptation of "Monte Makaya" in Brazil, with consultation from Tussauds attraction developer John Wardley. "Colossus" was the world's first roller coaster with ten inversions; an exact replica, called the "10 Inversion Roller Coaster", was later built at Chimelong Paradise in Guangzhou, China. It retained its title of having the most inversions on any other roller coaster in the world until "The Smiler" at Alton Towers took the record in 2013.
Document 11: Wooden roller coaster: A wooden roller coaster is most often classified as a roller coaster with running rails made of flattened steel strips mounted on laminated wooden track. Occasionally, the support structure may be made out of a steel lattice or truss, but the ride remains classified as a wooden roller coaster due to the track design. Because of the limits of wood, wooden roller coasters, in general, do not have inversions (when the coaster goes upside down), steep drops, or extremely banked turns (overbanked turns). However, there are exceptions; the defunct Son of Beast at Kings Island had a 214 ft drop and originally had a 90 ft loop until the end of the 2006 season, although the loop had steel supports. Other special cases are Hades 360 at Mount Olympus Water and Theme Park in Wisconsin Dells, Wisconsin. The coaster features a double-track tunnel, a corkscrew, and a 90-degree banked turn. There is also The Voyage at Holiday World (an example of a wooden roller coaster with a steel structure for supports) featuring three separate 90-degree banked turns. Ravine Flyer II at Waldameer Park has a 90-degree banked turn, T Express at Everland in South Korea with a 77-degree drop, and Outlaw Run at Silver Dollar City which has 3 inversions and 120-degree overbanked turn.
Document 12: Corkscrew (Alton Towers): Corkscrew was a steel roller coaster manufactured by Dutch company Vekoma to a design by Arrow Dynamics. The coaster was located in the Ug Land area of Alton Towers in Staffordshire, England. It was the park's oldest ride and is considered the greatest factor in promoting the new theme park to the British public. It was one of the first double-inverting coasters in Europe (the first in the UK), so it received much publicity and avid popularity in the 1980s. Waiting times for the ride frequently reached 6–9 hours during the first few months of operation at Alton Towers, and the park would often be forced to close early as it found itself swamped with visitors long before the evening ever came.
Document 13: Steel Eel: Steel Eel is a custom roller coaster built by D. H. Morgan Manufacturing. At a height of 150 feet, "Steel Eel" is the tallest roller coaster at SeaWorld San Antonio and was the second coaster built by SeaWorld, following The Great White (1997), after new management felt the park needed to offer more thrilling rides. "Steel Eel" had to be custom built to fit along the slim area beside the lake and utilizes a simple lapbar and seatbelt restraint system. Key elements of "Steel Eel" include two hills after the lift hill with a small valley between the two and a diving dogleg turn and triple humpback hills after its mid-course brake run. With a paint scheme consisting of bright yellow track and teal-green supports, it has become a permanent staple in the park's skyline.
Document 14: Roller coaster: A roller coaster is a type of amusement ride that employs a form of elevated railroad track designed with tight turns, steep slopes, and sometimes inversions. People ride along the track in open cars, and the rides are often found in amusement parks and theme parks around the world. LaMarcus Adna Thompson obtained one of the first known patents for a roller coaster design in 1885, related to the Switchback Railway that opened a year earlier at Coney Island.<ref>
Document 15: List of roller coaster rankings: Roller coasters are amusement rides developed for amusement parks and modern theme parks. During the 16th and 17th centuries, rides consisting of wooden sleds that took riders down large slides made from ice were popular in Russia. The first roller coasters, where the train was attached to a wooden track, first appeared in France in the early 1800s. Although wooden roller coasters are still being produced, steel roller coasters are more common and can be found on every continent except Antarctica.
ground_truth: eight