GRAHAM opens first stretch of Clifton Hampden Bypass to traffic after 62-hour switch

GRAHAM has opened part of the Clifton Hampden Bypass in Oxfordshire to cars for the first time, after a 62-hour weekend traffic switch six months on from its appointment to the £37m contract.

The switch went live on Monday 12 October, the contractor said. The team worked round the clock from Friday 9 October to complete excavation, pavement construction, drainage connections, road markings, signage and commissioning.

Three sites along the route, Culham Science Centre, the business area at Culham Site No.1 and Culham station, are now reached via newly built sections of highway. GRAHAM said the change also frees up existing stretches of road to be absorbed into the new bypass while keeping local connections in place.

John Deery, Project Director at GRAHAM, said: "It's a great feeling to see cars on the new road. A lot of work went into that weekend, and I'm proud of how the team and our supply chain pulled together to get it done."

The contract

The £37m Clifton Hampden Bypass will deliver a 2.2km single carriageway from the B4015 Oxford Road to the A415 at Culham Science Centre. Oxfordshire County Council describes it as a western bypass to the village, with two-way pedestrian and cycle facilities separated from the carriageway.

Once open, GRAHAM said, the road will take through-traffic out of Clifton Hampden village, including the area around the primary school. A new roundabout at the western end will serve Culham Science Centre and Culham railway station, according to the contractor's April 2026 appointment release.

The switch caps GRAHAM's first earthworks season on the job. Alongside cut and fill, embankment construction and formation preparation, the team has built a dedicated footpath giving pedestrians and cyclists access to Culham station and nearby bus stops. All five major culverts are in place, together with significant sections of the permanent drainage network.

GRAHAM said reaching this stage unlocks further construction areas, allowing the next phases of the bypass works to progress.

Councillor Liz Leffman, Oxfordshire County Council's Cabinet Member for Highways Construction and Repair, said: "The successful completion of the traffic switch marks a significant achievement for this section of the scheme". She added that the transformation across the site had been remarkable and she was pleased with progress.

The HIF1 programme

The bypass is one of three construction contracts in the council's Didcot and surrounding areas major infrastructure scheme, known as HIF1, which GRAHAM put at £332m. The council's scheme page says HIF1 comprises four highway sections, funded by Homes England grant, Enterprise Oxfordshire capital investment, Section 106 developer contributions and the council's own capital budget.

GRAHAM is building two of those sections. The contractor has also been appointed to the third and final HIF1 construction contract, the Didcot to Culham River Crossing: a 3.6km single carriageway between the A4130 at Collett roundabout in Didcot and the A415 at Culham, with new bridges over the Appleford railway sidings and the River Thames. GRAHAM said construction of the crossing is expected to last about two and a half years.

GRAHAM's HIF1 roads	Length
Clifton Hampden Bypass	2.2km
Didcot to Culham River Crossing	3.6km

Deery said the bypass and the river crossing "are two parts of the same picture".

Background

GRAHAM's involvement predates both construction awards. Andrew Henry, GRAHAM Contracts Director, said in February 2025 that the firm had worked with the council since April 2023 through early contractor involvement. In that month the council contracted GRAHAM for detailed design of the Culham river crossing and Clifton Hampden bypass, with AECOM designing the Didcot Science Bridge and A4130 widening.

The scheme went through a 21-day conjoined public inquiry in 2024. The council announced on 16 December 2024 that the Secretary of State for Housing, Communities and Local Government had granted planning approval following a planning inspector's recommendation, and said the £332m project was fully funded, with additional Homes England grants secured in 2022 and 2024.

Pauline Schaffer, Director – Infrastructure Funding at Homes England, said at the time of GRAHAM's April 2026 appointment that the Housing Infrastructure Fund investment was helping bring forward the Didcot scheme and unlock new homes.

The council's 20 April 2026 release recorded enabling works, including site clearance, archaeology investigations and utility diversions, already under way. GRAHAM said at appointment that main construction was expected to start in spring 2026 and last about two years.