Dual-Mode Road-Rail Fire Truck: Versatile and Efficient
The road-rail fire truck is mainly used for firefighting along urban rail lines, utilizing the tracks for fast and precise mobility.
This particular Unimog U423 has been modified into a fire truck and now features significantly more external equipment. On the front is a Ziegler fire monitor with a pressure of 1.0 MPa and a flow rate of 25 L/s, along with additional water-spraying equipment mounted below.
The bumper of the U423 has a unique structure, surrounded by circular steel tubing. The left and right ends house independent headlights, with the left panel also reserved for a hydraulic power interface.
At the lower front of the vehicle, a set of rail guiding wheels is installed with a standard Chinese track gauge of 1,435 mm. These guide wheels function similarly to mechanical lift axles and are adjusted using a hydraulic system. However, they are not driven and serve only for guidance during rail operation.
The rail system is supplied by Germany’s ZAGRO, a specialist in railway shunting and dual-mode technologies. Their rail products span various sectors, including firefighting, as seen in this application.
The vehicle still relies on traditional wheels for movement, though the design has been adapted. The U423’s wheels are fitted with convex rims to align the tires with the rail tracks, using friction to drive the vehicle forward or backward on rails.
The U423 remains a 4WD vehicle and uses a unique portal axle system, with disc brakes for stopping power.
Both front and rear wheels share the same rim specifications. A set of retractable rail guiding wheels is also mounted at the rear.
At the end of the chassis, a pair of hydraulic support rods is installed. When rail travel is required, the hydraulic rods push the guiding wheel assembly down. This assembly is connected below the frame and operates axially when the hydraulic rods engage. The system is simple and easy to maintain.
There is also an alternative guidance setup for the Unimog, which places a pair of rail guide wheels at the front and rear of each axle. This H-type bogie system is installed on the chassis and operates via a lifting mechanism, better suited for tracks with smaller turning radii, such as light rail systems.
At the rear, the vehicle is equipped with taillights, a water inlet, electrical connectors, a towing ring, and more. The vehicle can also be equipped with a hydraulic torque converter, allowing it to tow train cars if needed—something Unimogs are already known to do in rail shunting roles abroad.
Powering the vehicle is an OM934 LA inline 4-cylinder engine with a 5.13L displacement, delivering 231 horsepower and 900 N·m of torque. It’s paired with a UG-100 8-speed transmission, allowing a top road speed of 90 km/h. On rail, its speed is capped at 30 km/h.
Both sides of the 3000L Unimog U423 4WD Road-Rail dual-use water foam fire truck are fitted with 3-step stamped boarding ladders. Due to its compact size, the chassis is densely packed. On the right side, the steps enclose the hydraulic tank and air filter. Behind them are the cab lifting system, DEF tank, and EURO VI aftertreatment system.
Opening the door reveals a simple, standard seat inside the cab, with optional air suspension seats.
The U423‘s cab resembles a tractor design, featuring large front and side windows for excellent visibility.
The side windows are almost floor-length, and the side mirrors are positioned near the driver’s legs, giving the windows a very distinct design. All vehicle controls are integrated inside the cab with a dense layout of levers and buttons, allowing full operation without opening the doors.
The dashboard and display use a floating design. Sitting in the U423 cab feels less like a truck and more like operating a large agricultural machine like a harvester, thanks to the panoramic view. Yet, the firefighting equipment brings you back to reality—this is a battle-ready emergency vehicle.
The steering wheel and dashboard adopt Mercedes-Benz‘s latest designs for their trucks and commercial vehicles. The steering wheel features the new Actros 4-spoke layout, with multifunction buttons on both sides. The floating instrument panel behind it also follows the Mercedes family design, and the headlight switches use rotary knobs.
In addition to the front-mounted fire monitor, this Unimog U423 road-rail fire truck is also equipped with another fire cannon capable of delivering 600 to 4,500 L/min.
The compartment can carry 2,000 liters of liquid and 200 liters of firefighting foam. This setup allows the vehicle to be among the first responders, effectively containing fires in their early stages.
A power take-off shaft extends from the engine to drive the onboard water pump. A key feature of the Unimog is that its superstructure operates independently of vehicle movement—meaning the PTO and fire systems can work while the vehicle is in motion.
With all these capabilities, the 3000L Unimog U423 4WD Road-Rail dual-use water foam fire truck has always been favored in the vehicle modification industry. As urban rail systems continue to expand, demand for this type of road-rail fire truck is expected to grow significantly.
