An £18.4m road will tackle "huge" traffic problems around a Somerset town, according to the local authority.
Construction work has started on the Colley Lane Southern Access Road (CLSAR) in Bridgwater.
EDF Energy contributed £2m towards the cost as part of its "commitment to support local communities" living around Hinkley Point.
Somerset County Council said congestion problems were partly caused by traffic to the new power station site.
David Eccles, EDF's head of stakeholder engagement, said: "Congestion in Bridgwater has been getting steadily worse over many years as the town has grown and become more prosperous.
"EDF has already delivered around £20m of road improvements in and around the area".
The 840m-long relief road will cost an estimated £22,000 per metre to build.
The project will also see two new bridges, cycle paths and footways constructed as well as providing access to brown-field development sites where new housing is planned.
Thousands of travellers driving up and down the M5 corridor are also likely to benefit.