UK How a hi-rail vehicle works
A hi-rail vehicle is an ordinary road vehicle with a set of small steel rail wheels, the hi-rail gear, mounted front and rear. On the road the gear is folded up out of the way. At a level crossing or a dedicated access point, the driver lines the vehicle up with the rails and lowers the gear hydraulically. The flanged guide wheels then keep the vehicle on the track, much as the wheels of a train do.
On many hi-rail trucks the road tyres stay in contact with the rail and still provide drive and braking, while the guide wheels steer. On heavier machines the rail wheels themselves are driven. Either way, the vehicle can leave the road, work on the line and return to the road without a trailer or a crane. That is the advantage over rail-only equipment, which has to be moved to site by rail and fitted into the railway’s timetable.
In North America the term is hi-rail, from highway-rail. In the UK and much of Europe the same vehicles are called road-rail vehicles, or RRVs, and are treated as on-track plant.
Types of hi-rail vehicle
Almost any road chassis can carry hi-rail gear, so the fleet on a large railway covers a wide range of work.
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Hi-rail pickups and SUVs. The most common type. Used by track inspectors, signal technicians and supervisors to patrol the line and reach work sites quickly.
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Hi-rail trucks. Heavier chassis carrying cranes, booms, dump bodies, welding equipment or rail-handling gear for maintenance gangs.
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Road-rail excavators. Tracked or wheeled excavators with rail gear, widely used in the UK for ballast, drainage and vegetation work.
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Overhead line vehicles. Trucks with elevating work platforms for inspecting and repairing electrification equipment.
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Inspection and measurement vehicles. Hi-rail trucks fitted with cameras, LiDAR, ultrasonic rail flaw detectors or track geometry systems.
Hi-rail vehicles compared with other track equipment
Railways inspect and maintain track with a mix of road-rail and rail-only equipment. Each has a different trade-off between flexibility and capacity.
| Equipment | Reaches site by | Typical work | Track access |
|---|---|---|---|
| Hi-rail pickup or van | Road, then on-track at a crossing | Patrols, visual inspection, small repairs | Short possessions or track authority |
| Hi-rail truck | Road, then on-track | Maintenance, lifting, materials, measurement | Possession or work window |
| Road-rail excavator | Low-loader, then on-track at an access point | Ballast, drainage, civils | Possession, usually overnight |
| Track recording train | Rail only | High-speed geometry and condition surveys | Timetabled path between services |
Hi-rail vehicles are usually light enough that they may not reliably operate track circuits, the electrical circuits that tell the signalling system a train is present. That is why their movements are protected by a track authority, a possession or similar rules rather than by the signals alone.
Hi-rail track inspection
Visual track patrols from hi-rail vehicles are a routine part of rail maintenance. In the US, the track safety standards allow an inspector to ride over the track in a vehicle at a speed that lets them see what they are inspecting. Manual patrols are slow and expensive, they put staff on or near live track, and inspectors face a heavy workload watching for defects over long distances.
Fitting sensors to the vehicle changes how that work is done. The crew still drives the route, but the data is captured automatically, analysed by AI and reviewed later, which gives a consistent record of every kilometre. A typical inspection set-up includes:
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Forward-facing and downward cameras. High-resolution video of the rails, sleepers, fastenings and the corridor alongside the line.
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LiDAR. 3D measurements of clearances, vegetation, structures and ballast profile. Our LiDAR FAQ explains how it measures.
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GNSS and IMU. Precise location and orientation for every frame, so each defect is tied to a point on the network.
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Rugged computer. Captures and processes the data on board, rated for vehicle power, shock and vibration.
Computers for hi-rail and road-rail vehicles
An inspection computer on a hi-rail vehicle has to cope with both worlds. On the road it sees vehicle power, engine cranking and the vibration of a truck chassis. On the track it sees the rail environment, and when it is used on a railway’s own fleet it may need to meet rolling stock standards such as EN 50155. Our guide to EN 50155 certification covers what that means.
Our railway computers and in-vehicle computers cover both cases, with wide DC input, ignition control, PoE for cameras and GPU or Jetson processing for AI. The railway track inspection case study shows an automated alternative to manual hi-rail patrols, and the same data can feed a digital twin of the railway corridor.
Quick answers on hi-rail vehicles
Hi-rail vehicles: common questions
What is a hi-rail vehicle used for?
Getting crews and equipment onto the track quickly. Inspection, maintenance, signalling and electrification teams use them to reach work sites by road and then travel along the line.
Is a hi-rail the same as a road-rail vehicle?
Yes. Hi-rail is the North American name and road-rail vehicle, or RRV, is the usual UK term. Both describe a road vehicle with rail guide wheels.
Can anyone drive a hi-rail vehicle on the track?
No. Operators need railway training and the railway’s authority to occupy the track, and in the UK road-rail vehicles must be accepted as on-track plant before use.
How fast can a hi-rail vehicle travel on rails?
Much slower than on the road. The limit is set by the railway’s operating rules and the rating of the rail gear, and is lower again over switches, crossings and during inspection.
What is a hi-rail truck?
A larger road truck with hi-rail gear. It carries a crane, dump body, boom or materials, rather than just a crew.
We supply railway and in-vehicle computers configured for hi-rail inspection as standard, with the cameras, GNSS and storage integrated and validated before the system ships.