It runs between the British university cities of Oxford and Cambridge via Milton Keynes and other settlements in Bedfordshire, Buckinghamshire, Cambridgeshire, Northamptonshire, Oxfordshire at the northern rim of the London commuter belt.

The original Oxford to Cambridge (O2C) Arc initiative was launched in 2003 by three English regional development agencies (RDAs), EEDA, EMDA and SEEDA.

[3] In January 2025, Chancellor Rachel Reeves confirmed funding for the Bedford–Cambridge section of the railway,[a] stating her view that the "Oxford–Cambridge Growth Corridor" has the potential to become "Europe's Silicon Valley".

[c] In 2017, the National Infrastructure Commission projected that the Arc will become host to major hi-tech industrial developments and will need to provide one million new homes by 2050, with Milton Keynes alone doubling in population to 500,000.

Detailed route options planning began on the Oxford-Milton Keynes phase that was to complete the Oxford-Cambridge Expressway (linking the A34 south of Oxford with the A14 near Cambridge).

Bedford, roughly central to the Arc and with a population of 100,000, is home to native speakers of over 100 languages, a figure which rivals London, Birmingham, Leeds and Manchester.

The Arc has the fastest growing population of any of the similar regions within the UK; several of the major towns and cities, most notably Bicester and Milton Keynes, are set to double in size over the coming few decades,[7] and others, such as Cambourne, have been built from scratch since the late 1990s.

In November 2017, in its report on the Arc, the NIC called for the railway line between Bicester and Bletchley to be reopened by 2023 and a new route between Bedford and Cambridge to be operational by 2030, and for the development and construction of a new grade separated dual carriageway between the M1 and Oxford by 2030, as part of a new Oxford–Cambridge Expressway.

[8] As of July 2022[update], the route through Bedford to Cambridge is still in detailed planning but the Minister has cast doubt on whether earlier commitments will be honoured and construction proceed.