Road-rail vehicle

A road–rail vehicle is a vehicle which can operate both on rail tracks and a conventional road. They are also called hi-rail, from highway and rail, or variations such as high-rail, HiRail, Hy-rail, etc.

They are often converted road vehicles, keeping their normal wheels with rubber tires, but fitted with additional flanged steel wheels for running on rails. Propulsion is typically through the conventional tires, the flanged wheels being free-rolling; the rail wheels are raised and lowered as needed. Purpose-built road–rail vehicles also exist.

Such vehicles are normally used for railroad right-of-way maintenance during engineering possessions of the line. They can be driven on roads to near the site and then convert to rail vehicle for the final journey to the worksite. This avoids the complex maneuvers that would be associated with a road vehicle accessing the worksite if the worksite is not near a road. Since they are normally converted road vehicles, they would not fare well in a collision with heavy rolling stock and therefore can normally only drive on rail tracks under an engineering possession (the line is closed to normal traffic). They are generally designed to be insulated, thus they do not activate track (signaling) circuits although some rail operators, normally those operating remote lines without boom gates etc. prefer them to be non-insulated so that they are detectable by train safety systems.

Attempts have been made over the years to design buses and coaches that could operate on both roads and railway tracks. These attempts were never particularly successful. Some were carried out in Britain during the 1930s, on the Nickey Line by LMS, using a Ro-Railer. In Australia, the New South Wales Government Railways tried road–rail vehicles during the 1970s on New South Wales routes.

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Wikipedia