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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. The rail wheels are raised and lowered as needed. Purpose-built road-rail vehicles also exist.
Road-rail technology is believed to have been developed by Fairmont Railway Motors in the 1940s to improve flexibility of vehicle use. Fairmont's key product, motor section cars, limited the ability for maintenance crews to travel. Fairmont was bought by Harsco in the late 1980s.
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 a heavy rolling stock and therefore can only drive on rail tracks under an engineering possession. They are generally designed to be insulated, thus they do not activate track (signaling) circuits.
Road Rail buses
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 Nicky Line by LMS, using a Ro-Railer. In Australia, the New South Wales Railways tried road-rail vehicles during the 1970s on New South Wales routes.
The RTL is a truck prime mover with railway wheels that can be lowered when operating on the railway tracks. It was pioneered by in the early 1990s by Australian National and later refined in Victoria. The idea was to have a locomotive that could transfer from one branch line carrying mainly wheat to another parallel branch line, where the rail connection is very roundabout. The RTL suffered a number of disadvantages. Loads were severely limited when the track was steeply graded. The rubber traction wheels slipped on the steel rails when wet. The life of the rubber tires was rather short.
The Canadian company Brandt has also converted large truck tractor units for use as locomotives that can move by road to where they are needed. Still mostly used for permanent way maintenance, they can also be employed as thunderbird (rescue) locomotives or even used in normal service, where they are suitable for smaller operators.
In Belgium, the company UCA produces the UCA-TRAC, rail/road vehicles based on the chassis of a JCB Load-All (UCA-TRAC B) and JCB Fastrac (UCA-TRAC F). The UCA-TRAC provides traction through its rubber wheels.
Self-propelled maintenance vehicles for maintenance of the track and for shunting wagons are much more convenient to use if they can transfer to the road to reposition or otherwise get out of the way. Because relatively light loads are involved, the problems plaguing the Road Transferable Locomotive are avoided.
An example would be a forklift truck fitted with railway wheels and a coupling with which to shunt a wagon or two.
In Belgium, the company UCA bvba has been constructing rail/road vehicles since 1981. UCA started with converting WF-trac and MB-trac for rail traction uses. They built rail car movers, shunting locotractors and other rail/road vehicles. Best known is the UCA-TRAC, based on the chassis of a JCB Load-All (UCA-TRAC B) and Fastrac (UCA-TRAC F). The UCA-TRAC provides traction through its rubber wheels.
Road rail vehicles, particularly those used for inspection purposes, have been involved in a number of serious incidents, including deaths. There has been ongoing discussion[clarification needed] regarding maintenance and inspection standards, including load and load distribution, to minimise the risk of failures.
Factors leading to derailment include failed locking equipment, wheel failure, damaged rail wheel support systems, inappropriate tires, and uneven or over-loading issues.
"Evans Auto-Railer" was a pioneer in the US in the 1930s and 40s. Evans seems to have produced all road/rail vehicle adaptations for the U.S. Military during WWII, but were rapidly overtaken by Fairmont immediately post-war.
Some vehicles were adapted so as to be able to run on rail tracks only.
A road-rail excavator
A road-rail scissor lift
A road-rail excavator in Muurame, Finland
A "dual mode vehicle" used by the Hokkaido Railway Company
HiRail wheel (retracted) on a Dodge Dakota
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