Plans to build a bypass over a traffic "bottleneck" will go ahead after officials agreed extra funding of more than £16m.
It emerged earlier this month that the cost of the bridge over the King's Dyke rail crossing near Peterborough had doubled to £30m.
Cambridgeshire County Council leader Steve Count said the new road would bring "economic prosperity".
Construction firm Kier is due to begin the work next spring.
The bypass will connect Peterborough and Whittlesey, with a bridge planned over the main Ely to Peterborough railway line.
The extra money was approved by the Cambridgeshire and Peterborough Combined Authority on Wednesday, headed by mayor James Palmer.
A spokesman for the county council said they approached the authority for the additional funding after "detailed designs" meant it would cost more than initial estimates.
Mr Count said the road would bring "huge benefits".
"The current level crossing has been a bottleneck for a long time," he said, "with slow moving freight trains causing an average minimum delay of 13 minutes and often very much longer.
"This is bad for local people and bad for the economy of the area."
The new road and bridge are expected to open to traffic by late 2020.