Tandem in the tunnel.

The Unimog in action for GVB Amsterdam for towing metro trains.

GVB, the Amsterdam municipal public transport corporation, is responsible for urban buses, ferries, the Metro and the tram network in the capital of the Netherlands, transporting approximately 875.000 passengers each working day. Recently the huge fleet of the GVB has had two new additions: two road-rail vehicles based on the Unimog U423 for maintenance and emergency operation; these ensure that rail traffic runs smoothly, in particular for the infrastructure of the new M52 underground line, which went into operation in 2018.

Doubling the tractive force by means of tandem traction.

One special feature of the road-rail vehicles which were converted by ZAGRO is the possibility of coupling the Unimog vehicles in an emergency, thus almost doubling the tractive force. This means that a metro train 120 m long and weighing approx. 200 t, on a gradient of over 4 %, can be towed effortlessly, for example out of a tunnel.

"For this tandem operation, the Unimog vehicles are coupled both mechanically and electronically, so by means of precisely matching the revs, optimum tractive force can be achieved," explains Matthijs Bokma from the Koks Group, the Dutch sales partner of ZAGRO. Only the Unimog at the front has a driver; the Unimog coupled behind is automatically controlled by a system made by ZAGRO.

In order to achieve this tractive output, both Unimog U423 vehicles are equipped ex works with a torque converter clutch and the necessary electronic interface. Adequate tractive power on the rails is also provided by the special Unimog wheels, and the ZAGRO rail gear keeps them safely on the track. The total length of the M52 is 9.7 kilometres, 7.1 km of which are underground, so equipping the Unimog with environmentally friendly Euro 6 engine technology was an important aspect for G


Tailor-made and cost-effective.

According to Gijs Brink, Projectl Manager at GVB, coupling the Unimog vehicles in tandem in an emergency will, hopefully, only be necessary very rarely. That is why the Unimog vehicles were designed as flexible working vehicles which can be used individually for a wide variety of tasks on the GVB rail infrastructure. The Unimog U423 with a loading crane and a wagon brake system for 400 t , which was delivered back in 2017, proves its worth daily when the metro trains are not running; it is used for example for replacing points or towing working machinery on the rails.

The Unimog U423 which was handed over to GVB in March 2019 at the RailTech Europe exhibition, with a box body, a wagon brake system and hydraulic rerailing equipment, can be used flexibly by GVB.

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