What is "hovertrain"

n. A train that uses hovercraft technology to take advantage of lower friction to deliver high speeds; an aerotrain.

A hovertrain is a type of high-speed train that replaces conventional steel wheels with hovercraft lift pads, and the conventional railway bed with a paved road-like surface, known as the track or guideway. The concept aims to eliminate rolling resistance and allow very high performance, while also simplifying the infrastructure needed to lay new lines.

Hovertrains were seen as a relatively low-risk and low-cost way to develop high-speed inter-city train service, in an era when conventional rail seemed stuck to speeds around or less. By the late 1960s, major development efforts were underway in France, the UK and the USA. While they were being developed, British Rail was running an extensive study of the problems being seen at high speeds on conventional rails. This led to a series of new high-speed train designs in the 1970s, starting with their own APT. Although the hovertrains still had reduced infrastructure costs compared to the APT and similar designs like the TGV, in practice this was offset by the fact that they needed entirely new lines. Conventional wheeled trains could run at low speed on existing lines, greatly reducing capital expenditures in dense areas. Interest in hovertrains waned, and major development had ended by the mid-1970s.

Hovertrains were also developed for smaller systems, including personal rapid transit systems that were a hot topic in the late 1960s and early 1970s. In this role their ability to float over small imperfections and debris on the "rails" was a practical advantage, although it competed with the maglev concept that had the same advantages. The only hovertain to see commercial service was the Otis Hovair system. Originally developed at General Motors as an automated guideway transit system, GM was forced to divest the design as part of an anti-trust ruling. The design eventually ended up at Otis Elevator who later replaced its linear motor with a cable pull and sold the resulting design for people mover installations all over the world.

Hovertrain is a generic term, and the vehicles are more commonly referred to by the projects that developed them in different countries – in the UK they are known as tracked hovercraft, in the US they are tracked air-cushion vehicles, and in France they are the aerotrains. News sources often conflate maglev trains with hovertrains, as both are levitated above the running surface, "hovering" over them.