The Calcutta Metro has started replacing the steel third rails in its oldest corridor with the ones made of aluminium, which will ensure an 84 per cent reduction in energy consumption, officials said on Friday.

The third rail system provides power to a train through a conductor kept alongside the rails, they said.

"Once completed, Kolkata Metro will join Singapore, London, Moscow, Berlin, Munich and Istanbul where such replacement work of third rail has already been done and services are on smoothly," an official said.

The change shall ensure savings of Rs 1 crore per year per km, he said.

The highly conductive aluminium third rail with stainless steel top will replace the existing steel-made third rail from Dum Dum station to Mahanayak Uttam Kumar station in Tollygunj in the North-South Line.

The tender has been awarded to a Germany-based company and the work will be completed in two years, the official said.

The aluminium third rails would reduce carbon emissions by 50,000 tons in its lifetime, he claimed.

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