A public inquiry into Halton's Mersey Gateway Bridge is finally underway and is expected to last six to ten weeks.
Those involved in the project predict that a decision will be announced later in the year.
If approved, construction work would begin in 2011, with the target being to open the new toll bridge in 2014.
Plans were put forward to the Secretary of State in July 2008 after Halton councillors gave the scheme their backing.
However, the Department for Transport called in plans last October on the £431m bridge proposed to be built across the River Mersey.
The inquiry is being led by Inspector Alan Gray and is being held at Halton's Stobart Stadium.
Following evidence from Halton, the team behind the Mersey Gateway project and objectors, the inspector will then make a recommendation to the Secretary of State as to whether the proposed plans should go ahead.
The second crossing would ease congestion currently experienced by users of the existing Silver Jubilee Bridge. The bridge will offer three lanes in each direction, roughly 1.5 km to the east of the first crossing.
The project includes modifications to the Silver Jubilee Bridge to improve facilities for public transport, walking and cycling. The scheme would also see new leisure, housing, and office premises built in Widnes and Runcorn to regenerate parts of the towns. Large areas of land would be cleared and compulsory purchase orders would be used to buy land along the route so that the project could go ahead.