Question: Derby Racer was the name of how many wooden roller coasters that operated at Revere Beach in Revere, Massachusetts, both coasters were racing roller coasters, with side-by-side track pairs where two coaster trains would race each other around the circuit of the coaster, a roller coaster train is a vehicle made up of two or more cars connected by specialized joints which transports passengers around a roller coaster's circuit?
Context: Derby Racer was the name of two wooden roller coasters that operated at Revere Beach in Revere, Massachusetts.  The first coaster was built in 1911 and demolished in 1936.  The second coaster of the same name was built in 1937 and demolished in 1948.  Both coasters were racing roller coasters, with side-by-side track pairs where two coaster trains would race each other around the circuit of the coaster. Hoosier Hurricane is a wooden roller coaster at Indiana Beach in Monticello, Indiana.  The ride was designed by Dennis McNulty and Larry Bill of Custom Coasters International.  It opened on May 27, 1994, as the park's largest wooden roller coaster and the first wooden roller coaster built in Indiana in fifty years.  The ride was Custom Coasters International's third roller coaster designed and the first modern wooden coaster built with a steel support structure, which would eventually become a trend on many wooden coasters designed by them. A roller coaster train is a vehicle made up of two or more cars connected by specialized joints which transports passengers around a roller coaster's circuit. The Cyclone was a wooden roller coaster that operated at Revere Beach in Revere, Massachusetts, from 1925 until 1969.  When Cyclone was constructed, it was the tallest roller coaster ever built, as well as being the first roller coaster in the world to reach 100 ft in height.  In addition to being the tallest roller coaster of its day, some also claim that it was the largest and fastest roller coaster in the world, with a length of 3600 ft and top speeds between 45 and 50 mph (some dispute the speed record claim and instead award that honor to the Giant Dipper).  Cyclone held the title of world's tallest roller coaster until 1964 when it was surpassed by Montaña Rusa at La Feria Chapultepec Mágico in Mexico City, Mexico. Kings Island is a 364 acre theme park located in Mason, Ohio, 24 mi northeast of Cincinnati.  Since the opening of the amusement park in 1972, at least one attraction has been added every year except 1978, 1980, 1983, and 2008.  The park is known to have attractions such as Flight of Fear which was the world's first linear induction motor launched roller coaster, and The Beast which has held the record for the world's longest wooden roller coaster since its opening in 1979.  Also, The Beast continues to be ranked as one of the best wooden roller coasters in the world by industry polls.  Kings Island's newest attraction is Mystic Timbers, a wooden roller coaster manufactured by Great Coasters International.  With this addition, Kings Island claimed the record for most wooden roller coaster track of any amusement park in the world, and tied the record for most wooden roller coasters, with five. Temple of the Night Hawk is an enclosed roller coaster located at Phantasialand.  Founded in 1988 after 18 months of construction, the ride was originally called ‘'Space Center'’.  The ride led passengers past models of rockets and emulated asteroids and the darkened hall was dimly lit with thousands of tiny spots of light to resemble stars.  Due to the construction of the neighbouring Wurze Town in 2001, the roller coaster was redeveloped with a fantasy jungle theme and was renamed as the "Temple of the Night Hawk".  The roller coaster is now completely dark.  Until 2006 there were some green moving lights and strobe lights in the first lifthill, still present today, but not operational.  In 2008 the Lights on the coaster trains were turned off or broke down and have never been repaired since then.  Till 2010 there was a green laser projection with the outlines of a flying hawk and until June 2012, there were some red strobe-lights at the final brakerun.  In 2011, the park installed new strobe lights in the first lifthill, which broke down after about two months, and were never repaired since then.  The ride has four trains and one spare train for repairs each with seven cars.  Each car has two rows of seats each holding two people.  During the four-minute ride time the trains are lifted by three lift hill chains, 1.174 metres of track.  The roller coaster is therefore one of the longest indoor roller coasters in the World, slightly beaten by "Mindbender" in Galaxyland Amusement Park, Canada.  The hall in which the track is located is around 120,000m³ in size and rests on 180 concrete pillars which are 12 metres deep in the ground.  In the basement of the hall is the ‘'Hollywood Tour’' darkride.  The total investment for the ride was around 15 million DM. 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. Roller coaster phobia is a colloquial and slang term describing an individual's fear of roller coasters.  While roller coasters are the most popular theme park attraction, certain people feel nauseated, afraid, dizzy, or unsafe when riding roller coasters.  In the majority of cases, this fear is related to acrophobia, claustrophobia, or a traumatic event.  Roller coaster phobia can be overcome relatively easily, the best cure being going on the tallest/fastest roller coaster before riding roller coasters of a lesser magnitude.  Roller coaster phobia has been linked to previously experiencing an accident, vertigo, and fear of heights.  In rare cases, riders may be afraid of roller coasters due to a painful ride, tight restraints, being thrown around in the restraints, and excessive g-forces on the body of the rider. Dauling Dragon (Chinese: 木翼双龙) is a wooden roller coaster located at Happy Valley in Wuhan, Hubei, China.  It is China's third wooden roller coaster and its first racing roller coaster.  Although billed as a racing coaster, it contains elements that make it similar to dueling coasters, such as racing portions, head-on collision turn-arounds, and sections where the tracks weave around each other.  This is much like Lightning Racer at Hersheypark (however, Lightning Racer was manufactured by Great Coasters International). Lightning was a wooden roller coaster that operated from 1927 until 1933 at Revere Beach in Revere, Massachusetts.  It was one of the infamous Giant Cyclone Safety Coasters which were constructed by noted roller coaster engineer Harry G. Traver in the mid-1920s (the rides were, in fact, anything but safe, and became known as the "terrifying triplets").  Lightning was the only Giant Cyclone Safety Coaster not to bear the "Cyclone" name, as a roller coaster named Cyclone already existed at Revere Beach when Lightning was constructed in 1927.  The other two members of this group of coasters included the Crystal Beach Cyclone and the Palisades Park Cyclone (A fourth Traver roller coaster named Zip had a similar—but smaller—design and was installed at Oaks Amusement Park in Portland, Oregon).
Answer: two