The Preston Western Distributor road is being constructed on the west side of the city from the M55 motorway to a new junction with Blackpool Road at Lea.
The Lancashire County Council road scheme also includes two new roads connecting to the current and future development of thousands of homes in the Northwest Preston Strategic Housing Site.
It is scheduled to open in 2023.
Ecological measures include new bat roosts, ponds for great crested newts and toads, barn owl protection measures and new habitats for brown hares and hedgehogs. And the viaducts have been designed to help to reduce the impact on otter habitats at the Lancaster Canal and Savick Brook.
Local councillors and other dignitaries representing organisations that have helped fund the scheme were present for the turf-cutting ceremony yesterday – Lancashire County Council, Lancashire Enterprise Partnership, Preston City Council, South Ribble Council, Homes England and others were all represented.
Lancashire County Council leader Geoff Driver said: "This ambitious £207m scheme will transform the way people in the area live, travel and work. It will particularly benefit people who live or work around the city, as well as further afield, by helping them to get between the motorway network and the city more easily.”
Bruce Parker, Highways England’s head of planning and development for the northwest, said: “We’re delighted this project is getting underway with a £25m investment from us – representing our commitment to help deliver thousands of new jobs and homes in the area as well as reducing congestion at neighbouring motorway junctions.”