The giant form travellers (approximately 40m wide) are being assembled at the north and south pylons of the Mersey estuary, while the commencement of this work at the central pylon is still pending. They will act as moveable moulds for the steady hangover bridge deck spans, advancing from each pylon towards the centre.

Once assembled at ground level, the machines will be lifted to their height by a hydraulic system and fixed into place at both sides of the bridge pylons in order to concrete the first deck span (first voussoir).

Next, each form traveller will move towards the open centre, steadily and symmetrically creating the deck spans (voussoirs). As such, the deck will "grow" on each side of the pylon until the main bridge deck is complete.
As from and including the third pair of voussoirs, the deck will have a stay cable system connected to the pylon that will be installed as each voussoir is constructed.

The machines are expected to start work this spring.