During repair work to the Cassanawald Tunnel on the San Bernardino Pass, a Mercedes-Benz Unimog is being used to shunt an unusual configuration of construction equipment on railway freight wagons.

The road-rail Unimog U 406, built in 1971 and upgraded with Euro 4 emission standards, acts as a railway ‘engine' when pulling the heavy construction train weighing 60 t through the 1.2 kilometre long Alpine tunnel. The reliability and efficiency of the Mercedes-Benz Unimog has really impressed its operators who up to now have been using normal railway engines to do similar jobs.

The heart of the work train is the 19 m long ‘machine wagon' which carries machines for wet and dry spraying as well as 4 m high screens to provide protection during spraying work. The second freight wagon is fitted with a permanently fitted concrete mixer; the third carries the compressors; and the fourth wagon carries silos for construction materials.

The engine is vintage Mercedes-Benz Unimog which used to belong to the Swiss Army and has now been fitted with road-rail equipment by road-rail specialist Zwiehoff from Rosenheim, in Upper Bavaria. The additional equipment enables the vehicle to be operated easily on rails and the road and also makes it unbeatable for cost-effective and versatile operations such as shunting or getting to derailed trains and on-tracking.

The Unimog shunts the work train to where it is needed and copes with a track profile with gradients of up to 3% within the tunnel itself. Working in the tunnel with its engine operating, it is imperative that the Unimog meets the European exhaust emission Euro 4 standard, which has been achieved by fitting a particle filter and other engine modifications.

(Caption: While being used for driving , shunting or as a train in the Cassanawald Tunnel, the Unimog has to be wrapped up to protect it against the diluted concrete which is sprayed on the walls of the tunnel.)