Rising out of the Mersey - and visible on a clear day from Woolton Road in Gateacre - is the new Runcorn-Widnes bridge, which is due to open to traffic in the autumn of 2017. Bernie Carr is one of 30 volunteers who gives talks to schools and community groups about the project.

Bernie told us that, when it opened in 1961, the existing Silver Jubilee Bridge was designed to carry 11,000 vehicles a day, but it now carries 88,000. The new bridge will relieve congestion, improve the 'reliability and resilience' of the road network, kick-start five development areas in Halton, and improve air quality. Tolls will be charged, because the project - one of the biggest in the UK - is being paid for by Halton Council - one of the smallest local authorities - using largely private finance which will have to be repaid. A DBFO (Design Build Finance Operate) company called Merseylink has been set up to do the work.

Bernie explained the challenges that the bridge designers had faced: three canals and three railways to cross, a fast flowing river with a 6.5 metre tidal range and salt marshes on each side, with some of the most heavily contaminated land in the UK and an existing road network that had to be kept running. The solution chosen was a 'cable-stayed bridge' - the type now almost universal for new bridges worldwide - upstream from the existing bridge, about 1 km long with 1.5 km of elevated approach roads over the marsh. The cables supporting the road deck will be tied to three concrete 'pylons', all of different heights (115, 80 and 125 metres) which will be one of the bridge's most distinctive features. The height difference is because each pylon supports a different length of roadway, the location of the piers having been selected so as to minimise the scouring of the river banks by the tide.

Bernie described in detail the way in which the pylons had been constructed using poured concrete - no easy task, bearing in mind that they are hexagonal and tapering, and stand directly on the rock below the bed of the river. 12 months of the 42 month 'design and construction' period was spent building the coffer dams and the bases of the pylons. Altogether 1,500km of cable will be needed - "enough to stretch from Lands End to John O'Groats", we were told. Components for the bridge - and the staff responsible for building it - have been brought in from all over the world, but we were pleased to hear that the wire for the cables is being manufactured in Warrington.

Bernie talked about how the £2-a-car and £8 HGV tolls will be collected. There will be no toll booths, and users will have to pay by phone or online within 24 hours of crossing the bridge. People will be able to register as regular users (or 'free' users, in the case of Halton residents) to simplify the process. Finally, he explained that the existing Silver Jubilee bridge will be closed for a while, but will then reopen as a 'local' bridge (with the same system of tolls). Pedestrians and cyclists - who will be banned from the new bridge - will be able to use the old one free of charge.

Bernie left us well-informed about the project, and keen to find out more. Several members of the audience said that they would take up his suggestion of regular trips to the Visitor Centre in Widnes, which gives a panoramic view of the work in progress.