Highways major schemes - cost estimates vs outturn cost
Case reference FOI2025/01539
Received 6 August 2025
Published 18 December 2025
Request
Please provide the following commercial information for the completed major highway infrastructure projects listed below:
1. A14 Cambridge to Huntingdon Improvement
2. A1 Leeming to Barton Improvement
3. M4 Smart Motorway (Junctions 3–12)
4. M6 Toll
5. M25 Widening (Junctions 16–23 and 27–30)
6. A19 Testo’s Roundabout
7. A19 Norton to Wynyard Improvement
8. A1 Coal House to Metrocentre Widening
9. M1 Junctions 6a–10 Widening
10. A2 Bean and Ebbsfleet Junction Improvements
11. A556 Knutsford to Bowdon Dual Carriageway
12. M20 Junction 10a Improvement Scheme
13. M62 Junctions 10–12 Widening
14. A43 Corby Link Road
15. A46 Newark to Widmerpool Improvement
16. A2/A282 Dartford Improvement
17. A3 Hindhead Tunnel
18. M74 Completion Project (Scotland, if applicable under remit)
19. A46 Coventry Junction Improvement
20. A421 Bedford to M1 Dualling
For each project, please provide:
1. The initial approved cost estimate (e.g. Strategic Outline Business Case or Outline Business Case stage)
2. Any revised estimates (e.g. Full Business Case, contract award)
3. The final outturn cost (upon project completion)
4. The dates of each cost estimate and completion
5. A brief explanation (if available) for any significant variance between early estimates and the final outturn cost (e.g. scope changes, inflation, delays, unforeseen events)
Response
Please refer to the attached spreadsheet. Some points to note regarding the provision of the data:
• Robust cost capture began at the start of RP1 (Road Period 1 - 2015-2020).We do not hold the information requested for older schemes.
• Reasons for any cost increase over the lifecycle of a scheme has been tracked from the start of RP2 (Road Period 2 - 2020-2025). Information for schemes prior to this date is not available.
• The A46 Coventry junctions is one scheme to improve two junctions, Binleyand Walsgrave. The data provided is for Binley as Walsgrave has not yet started works. As such the reasons for cost increase on Binley has not been analysed by the team yet.
Documents
This is National Highways' response to a freedom of information (FOI) or environmental information regulations (EIR) request.
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