A multi-million pound bypass, which was first proposed about 70 years ago to help cut congestion, officially opened in Hertfordshire on Thursday.
The £43m Baldock Bypass project aims to re-route through traffic on the A505 away from the town centre.
The bypass includes three road bridges, three footpath/bridleway bridges, one underpass and the Weston Hills tunnel.
Herts County Council said the bypass was first proposed in the 1930s but priority was given to other routes.
Construction began in April 2004 and was completed six months ahead of schedule.
The council said the centre of Baldock was very congested with more than 22,000 vehicles passing through the town centre each day, although only 9% of those stopped in the town.
It is estimated that more than 25,000 vehicles will use the bypass every day by 2020, the council added.