When the new M1 - A1 link road was built in the mid 1990s, completing a high-speed through route between the port of Felixstowe and the Midlands, it was decided to give it a continuous number. The road was made up of the A604 and part of the A45, with some new construction. It should, according to the usual convention, have been an "A5x" road, but no suitable numbers seem to have been available. The number A45 remained with the western section of its original route. A604 was presumably not distinctive enough for such an important road. And so the route became the new A14. (It is worth noting that the A14 falls entirely within Zone 1 of the motorway numbering system).
The final section of the M1 - A1 link road from Catthorpe to Rothwell was opened on 15 July 1994 by John MacGregor, Transport Secretary. Contractor was Tarmac Construction Ltd, contract cost £35.62 million. The total cost of the M1 - A1 link road had been £210 million.
Junction numbers were provided from 1 to 35 (Cambridge east) during 2001, extended to Felixstowe (Junction 62) in early 2002.