TWO giant bridge building machines are poised high above the River Mersey to start work on the main bridge deck of the new bridge.

Construction teams used a hydraulic system to lift the two 270-tonne form travellers into place at the south pylon in the Mersey estuary.

The machines, which act as movable concrete moulds, are positioned 26 metres above the river bed.

Workers are now making preparations to cast the first part of the bridge deck from the south pylon, which will take place next month.

Three pairs of form travellers - one pair for each pylon - will be used to cast the spans between the three bridge pylons to create the 1km reinforced concrete bridge deck.

This is expected to take around 12 months to complete.

The form travellers will be lifted into place at the north pylon later this month, while the machines for the central pylon will be positioned in the summer.

The Mersey Gateway six lane tolled bridge is on schedule to open in autumn 2017.