Shuttle roller coaster

A shuttle roller coaster is any roller coaster that ultimately does not make a complete circuit, but rather reverses at some point throughout its course and traverses the same track backwards. These are sometimes referred to as boomerang roller coasters, due to the ubiquity of Vekoma's Boomerang coaster model.

The first shuttle coasters were in fact the first roller coasters ever built. Inspired by the so-called "Russian Mountains," these wheeled cars built on tracks found popularity in the early 19th century in Paris.

In 1884, the Switchback Railway opened at Coney Island, and consisted of a car that traveled on two tracks between two towers. It was the first roller coaster designed as an amusement ride in America. The next shuttle roller coaster to be built was the Backety-Back Scenic Railway, built in 1909.

The first two launched shuttle coaster designs were introduced in 1977 by competitors Arrow Development and Anton Schwarzkopf. Arrow built and opened three that year including Black Widow (now defunct) at Six Flags New England, Screamin' Demon (also defunct) at Kings Island, and Zoomerang at Circus World (now located to Fun Spot Amusement Park & Zoo). Arrow's models used an electric motor to launch the train. Anton Schwarzkopf went with a different design using a dropped weight as a launch mechanism. This design was known as the Shuttle Loop. The first three built by that company were King Kobra at Kings Dominion (now located at Hopi Hari in Brazil), White Lightnin' at Carowinds (now located at Gold Reef City in South Africa), and Tidal Wave at Marriott's Great America in California.

...
Wikipedia