Liebherr A 900 C ZW-Li/1031

Updated: August 2026 – An excavator with rubber tyres, standing in the middle of the track: for many people, that’s their first encounter with a road-rail vehicle. The Liebherr A 900 C ZW-Li/1031 is exactly that kind of machine – a road excavator that switches onto the track using retractable rail gear. This page explains the technology behind it, the typical jobs it does, and the features that let you spot a road-rail vehicle instantly.

What is the Liebherr A 900 C ZW-Li/1031?

It’s a road-rail excavator: a hydraulic excavator on a wheeled undercarriage that’s additionally fitted with rail gear. On the road it rolls along like any other piece of construction machinery; on the track, the rail gear lowers, lifts the machine and guides it along the rails.

The letters ZW (short for Zweiwege, meaning “two-way”) in the type designation stand for this road-rail equipment, while the first part names the manufacturer’s excavator series. It’s a type designation from construction machinery, not a class number under railway classification – if you’re looking for a logic like that used for locomotive classes, you won’t find one here. For an approach that still lets you work systematically through vehicles without a classic class number, see the guide to identifying rolling stock.

Road-rail technology: how the changeover works

Where the road-rail excavator fits into the build process

Major track renewals run with engineering trains: rebuilding machines, cleaning machines, material wagons and tamping machines form a closed chain. The road-rail excavator works alongside this – wherever that chain would be too cumbersome, too expensive, or simply inaccessible.

Criterion	Road-rail excavator	Classic engineering train
Approach	by road to the rail access point	over the rail network on an allocated path
Lead time	short, often scheduled at a day’s notice	long-term planning, fixed possession
Typical job size	one-off jobs, follow-up work, small sections	continuous renewal of long stretches
Material handling	spot handling with grab or bucket	continuous via conveyor chains
Visibility for onlookers	high – often seen at level crossings	mostly at night and within the closed track

For heavy-lift jobs beyond an excavator’s reach, a railway crane such as the Kirow KRC 810 / 1200 is used instead. As a road-rail machine on a comparable principle but from a different background, you’ll also find the Atlas 1604 ZW; for transport and assembly work on the track, the Robel GKW 315 is the equivalent on a pure rail undercarriage.

Marking: one vehicle, two sets of rules

Road-rail vehicles are a special case for markings, because they operate in two transport systems at once. For running on the track, they’re classed as an auxiliary vehicle and carry a twelve-digit vehicle number, whose first two digits are the UIC type code – 99 for auxiliary vehicles. Country code, vehicle-specific part and self-check digit follow after that.

This dual role also has practical consequences for operation. A road-rail vehicle has to satisfy both sets of rules at once: the requirements for road vehicles and those for vehicles on the track, from braking equipment through signalling to inspection of the rail gear. That’s why such machines aren’t improvised conversions but purpose-built, type-approved vehicles – even if at first glance they look like an ordinary excavator with extra parts bolted on. The road-rail technology itself comes from specialist suppliers such as PACTON. Build, conversion and maintenance of such machines is handled by specialist firms such as Gleisbaumechanik Brandenburg.

At the same time, the machine carries the markings of the construction firm operating it: company logo, internal machine number, often a road registration plate. In German track work you’ll come across names such as SPITZKE SE. For documentation, that means: when in doubt, note both identifiers – the railway number and the internal machine number – plus the company address and the date. Only that combination will still let you identify the machine years later, once it’s long since moved on to another firm.

In practice, the internal number is often far easier to read than the railway number, and it’s precisely that one that helps you recognise the machine again. Keepers and worksites change with contracts, hire arrangements and building programmes – treat every match as a snapshot in time.

Watching and photographing safely

What lies behind the ban on entering the track legally, and what the consequences of breaking it can be, is set out in the article on entering the track and the possible penalties – no legal advice, but a clear line. Photographically, the same rules apply to construction machinery as to trains: a three-quarter view rather than a head-on shot, flat light rather than midday sun, and a clean, tight frame rather than a picture that tries to show everything. The basics are covered in the guide to taking good photos of trains.

Common mix-ups

In short

The Liebherr A 900 C ZW-Li/1031 stands for an entire vehicle class worth getting your head around once: road-rail vehicles are construction machines that gain the track as a second running surface. They need no allocated path and no engineering train, but they do need access onto the track. They’re recognisable by exactly one feature – tyres and rail gear on the same vehicle. What they’re doing right now is given away by the attachment, and who owns them is given away by the address, which can change at any time.