Authority to consider third bridge over the Great Ouse
A local authority is to spend £400,000 looking at a third road crossing over the River Great Ouse at Huntingdon to ease traffic congestion.
Motorists can currently cross the river between Godmanchester and Huntingdon on the main A14 - or the 14th Century Old Bridge which runs parallel.
Critics say opening the area up with a third bridge would have a "dramatic" environmental effect.
Cambridgeshire's mayor James Palmer said "doing nothing is not an option".
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A feasibility study is now under way which will look at possible locations and costs of connecting the A14 and A14. Its findings should be published by March.
Mr Palmer, head of the Cambridgeshire and Peterborough Combined Authority, estimated the bridge would cost about £136m.
Supporters say another crossing would help relieve congestion in Huntingdon, Godmanchester and St Ives and mean fewer cars on the narrow medieval bridge.
Mr Palmer said the study will look at environmental impact, traffic issues and the opportunity to deliver more housing.
"It is very important to open up Fenland - it has been maligned and ignored for many years," he said.
"We have to make sure what we do is beneficial to the people of Cambridgeshire."
Paul Boothman, of the Great Ouse Valley Trust, said the impact of a third bridge "could be really dramatic" in an Area of Outstanding Natural Beauty.
"The scope of the feasibility study is so narrow," he said.
"We think it needs to be broadened to look at other options such as a railway extension, or the metro system."
Mr Palmer said the study will also pinpoint a preferred location for any proposed crossing - and a more accurate assessment of the cost.
The crossing is one of 12 "crown jewel" projects identified by Mr Palmer - others include dualling the A47, creating a Cambridge Metro system and a university in Peterborough.