The A415 at Clifton Hampden drops to 20mph on Monday for a year. The order gives the exact 414-metre extent the council's own newsletter leaves out.

A 414-metre stretch of the A415 at Clifton Hampden drops to 20mph on Monday 31 August, and the order that does it runs for a full year, to 31 August 2027.

It is the second speed cut on the same road in a fortnight. A 40mph limit over roughly 2,500 metres, from Culham to the edge of Clifton Hampden, came into force on 21 August and is expected to stay until 31 January 2028.

Both come from the HIF1 scheme, the programme of new roads around Didcot that includes the new Thames crossing at Culham and the Clifton Hampden bypass. Oxfordshire County Council made both orders on 17 August, under section 14 of the Road Traffic Regulation Act 1984, and published them through the Public Notice Portal.

Exactly where the 20mph applies

The council’s own project pages describe the 20mph only as being “near the Turnpike garage”. The statutory order is far more precise, and it is the order that is enforceable:

  • 60mph to 20mph, from the junction with High Street to the junction with Thame Lane, a distance of about 414 metres
  • 60mph to 40mph, from outside the property known as South Cottage to the junction with High Street, about 322 metres
  • Both on Abingdon Road, Clifton Hampden, which is the A415
  • In force from 00:00 on 31 August 2026 until 23:59 on 31 August 2027
  • Order reference TTRO 252
Diagram showing the 2,500-metre 40mph section from Europa School at Culham to South Cottage, a 322-metre 40mph section to the High Street junction, and a 414-metre 20mph section from there to Thame Lane
The two orders in sequence along the A415. Diagram by Abingdon Online, not to scale.

The separate 40mph order covers a much longer run: from a point adjacent to Europa School UK, at Culham, to a point roughly 50 metres east of South Cottage, about 2,500 metres in total. That one continues a restriction already imposed under a shorter-lived section 14(2) notice, and the council has said it intends to make the longer order rather than that it has made it. The restriction on the ground is real either way; the paperwork extending it is not yet final.

The council gives two different reasons

Oxfordshire County Council’s August project newsletter and its scheme page both say the 20mph is there “to facilitate safe access to the working area for the Thames Water upgrades to Culham Treatment Works”.

The order the council actually made says something else. Its stated reason is a “temporary speed limit reduction on the A415 to allow safe construction vehicle access to Thame Lane”. It names the HIF1 project as the work being supported, and the county council itself as the body carrying it out. Thames Water is not mentioned.

The dates and the speed match exactly, so this is one restriction described two ways. It still matters which is right. The two accounts name different work and a different organisation as the cause, which is what a resident would want to know when the year is up and the limit is either lifted or extended. The order is the document with legal force, and it attributes the 20mph to HIF1 construction traffic using Thame Lane.

What else is restricted on this stretch

Thames Water is running diversion works on the A415 between Europa School and Culham Station until 28 September, under a single lane closure with two-way temporary lights. The council says every set of temporary lights tied to the utility diversions runs between 7am and 7pm, with someone operating them on manual control. That is meant to stop them stranding traffic outside working hours.

Two footpath closures on this side of the scheme run far longer than the road works:

  • Thames Valley Path, footpath 183/11/80 at Culham, south of Zouch Farm between east Culham and the railway line, closed until 30 November 2027. The order states plainly that there is no alternative crossing nearby.
  • Clifton Hampden footpaths 171/6/10 and 171/4/10, west of the B4015 Oxford Road, closed from March 2026 for about 18 months, so until roughly September 2027, with a signed diversion.
  • Appleford’s public right of way north of the B4016 is closed and diverted on the same timescale.

Two more restrictions apply at the Didcot end of the scheme:

  • the A4130 Perimeter Road, between the Avon Way and Hawksworth roundabouts, dropped from 50mph to 30mph over about 1,370 metres on 24 August, also dated to 31 January 2028
  • overnight work on the eastbound A4130 with two-way temporary lights from 7pm to 6am, between 24 August and 25 September

Narrow lanes and a reduced limit on the approaches to Collett roundabout are due to stay until early 2027 while the new roundabout is built.

Why the work is happening now

The county council appointed GRAHAM on 3 August to build the Didcot to Culham river crossing, the third and final construction contract on the scheme. The crossing is a 3.6km single carriageway between the A4130 at Didcot and the A415 at Culham, with a bridge over the Appleford railway sidings and a bridge over the Thames.

Work on the ground has moved past preparation. The council’s August newsletter records progress on the crossing:

  • three full piers completed on the temporary causeway for the viaduct
  • topsoil being stripped south of the A415
  • a temporary haul road finished between the Thames and the north side of the Appleford sidings bridge
  • sheet piling due to start on the temporary cofferdams

On the Clifton Hampden bypass, kerbs are about to be laid around the Culham Campus roundabout “in preparation for the first traffic switch”.

The council’s stated case for all of it is that the existing river crossings through Sutton Courtenay, Culham and Clifton Hampden are old, congested and flood in winter. Both the river crossing and the bypass have a target completion of autumn 2028.

What it means for you

If you drive the A415 between Abingdon and the A4074, budget more time from Monday. A 414-metre 20mph section and a 2,500-metre 40mph section on the same route will cost minutes on every trip, and the 20mph is in place for a year.

Two practical points worth knowing:

  • The 20mph is enforceable from 00:00 on 31 August, a bank holiday Monday. It is not advisory.
  • Neither limit ends when this phase does. The 40mph is dated to 31 January 2028 and the footpath closures to late 2027, so this is the normal state of the road for the next two years, not a short closure to wait out.

If the works cause a specific problem outside your door, the contractors publish direct lines rather than routing everything through the council. GRAHAM covers the river crossing and the Clifton Hampden bypass on 02895 071 034 or civilscustomerrelations@graham.co.uk. VolkerFitzpatrick covers the Didcot Science Bridge on 07385 517608.

Our Abingdon roadworks and travel page tracks what is shut across the district week by week, and we cover the district’s planning decisions on our Abingdon planning news page.