The Pipeline Coaster

The Pipeline Coaster (also known as a "Heartline Twister Coaster") was a roller coaster developed by Japanese ride company TOGO. Pipeline roller coasters position riders between the rails, rather than above or below. TOGO was the first and only company to produce this type of roller coaster successfully. Although Utah's Arrow Dynamics and Switzerland's Intamin AG developed these types of coasters as well, they didn't catch on. Some of the drawbacks of these coasters included the need for large, uncomfortable over-the-shoulder restraints as well as poor wheel-to-track construction. Only five pipeline coasters operate today.

jumpjet.info

History
TOGO developed the first Pipeline coaster and the first recorded Ultratwister coaster built was in 1985 at LaQua amusement park in Tokyo, Japan called Ultra Twister. The ride became somewhat popular in Japanese parks, and one year after the first was built, Six Flags purchased one of these coasters for their Six Flags Great Adventure theme park, where it resided until 1990 when it was moved to Six Flags Astroworld until the park closed in 2005. This coaster would remain the only pipeline coaster in America. The American Ultratwister still exists, however it awaits possible future assembly at Six Flags America.
TOGO's model would be the only somewhat successful design. Six of these were made and were successful in small parks due to its small footprint. The ride inverts riders three times through three Heartline Roll elements and utilizes a special near-vertical lift hill. The lift hill would be prone to down time for maintenance and the Ultra Twister owned by Six Flags had its lift hill modified by Premier Rides to a less steep angle when it was moved to Six Flags Astroworld.
Throughout the early 1990s, Arrow Dynamics attempted to develop a pipeline roller coaster. Only one of these was built as a prototype at Arrow's facility in Utah. Plans for the coaster were scrapped altogether due to roughness and other factors. However, one was partially built at Alton Towers in the United Kingdom. In the early 1990s, John Wardley twice attempted to build one of these at the park. The second attempt was partially built, but then scrapped for the coaster Nemesis. The coaster was not completely finished due to Arrow's finance problems.
In the mid 1990s, Intamin AG built a spiral roller coaster in South Korea. Not much is known about the design, but only one of these coasters were built. The only Spiral Coaster ever built is currently located in Kuwait.

wikipedia.org