A421

The A421 is a major east-west road that forms part of the main route between Oxford and Cambridge (via Milton Keynes and Bedford.) It could be seen as having fallen on hard times, as it has now lost a good few miles of its original route, although in compensation it has been greatly extended at its eastern end.

Route

A421 approaching Bedford

Today's route starts at the Barleymow Roundabout on the A43, just south of Brackley. This road was the B4030 but has now assumed a more important guise. From here the road makes the short journey to Finmere where it meets its old route. The road generally follows the B4030 route except for a new section just to the south-west of Mixbury and for the final part before meeting the A4421 at the Finmere Airfield roundabout.

Finmere and its neighbour Tingewick have now been bypassed with a high quality dual carriageway in part, somewhat out of place in my opinion. Quickly we arrive at the western end of the Buckingham bypass and traverse this by five roundabout junctions, including one with the A413 with which the road multiplexes for one section. The road then follows a new alignment for around 500 metres before joining the old route of the B4034. Originally, Buckingham (and the A413) marked the eastern end of the A421.

After the roundabout with the B4033 from Winslow. The road has been largely improved to a good standard, and we start to cross Whaddon Chase. As the road approaches Tattenhoe and Far Bletchley, the original B4034 takes the route to Bletchley, whilst the A421 adopts the guise of H8 (Standing Way). We cross the A5 without a junction (a spur leads off to a GSJ on the A5 from the next roundabout) and head through the outskirts of Milton Keynes towards the M1, crossing it via junction 13. This section has been upgraded to dual carriageway in a piecemeal approach during the 2000s/10s, with the final link being completed in 2020, connecting Milton Keynes by a continuous dual carriageway to the M1 at J13.

The final stretch runs from junction 13 of the M1 to the Black Cat roundabout on the A1. As such it is an important trunk route linking the A1 and M1. Moreover a little further north on the A1 is the A428 which joins up with the A14. This forms a continuous route from the East-Anglian Ports to the South Midlands and also form a relief road to the M25.

The M1/A421 interchange has been updated, completed in 2012, to cope with a higher volume of traffic, and encourage the use of routes such as the A507, which now also has access to the M1 from that junction.

The road was also dualled between the M1 and the Bedford bypass, where there are several large distribution centres. This project opened in December 2010 and included an upgrade of the Bedford southern bypass, which was opened in the late 1990s as single carriageway. It is now dual-carriageway throughout with grade separated junctions with other routes, such as A6. Shortly after this the only significant landmarks on the road come into view. These are the massive hangers that were built in the 1930s to house airships.

After the Bedford bypass we're on the Great Barford Bypass (which opened as a separate scheme in 2006), running from Bedford to the Black Cat.

History

The original start of the A421 on what was then the A43

Originally, the road started at the current A34 and B430 junction at Weston-on-the-Green. Back then this was a simple fork, which later became a roundabout, with the single-carriageway A43 from Oxford to Northampton. From here the road runs virtually straight towards Bicester, passing Wendlebury on its way and arriving into Bicester from the south. Through Bicester it became a slow moving road through the town, meeting the A41 (now B4100) in the centre. It then escaped north under the Marylebone–Banbury railway line and out towards Newton Purcell. The road becomes quite wide here due to an age-old improvement. It then dived under the now-disused Great Central Railway at Finmere Station. The road, still following a straight course, arrived at Finmere, site of a huge market on the old airfield.

The old route has now changed, dramatically in some places. From Weston on the Green the road is now the dual carriageway A34 link to the M40. From there it is dualled all the way to the Bicester bypass and is part of the re-routed A41. Indeed, the A421 south of Bicester had become a spur of the A43 by the mid-1940s but regained the A421 number in the 1960s. North of Bicester the road has been imaginatively renumbered the A4421.

Opening Dates

Year	Section	Notes
1939	Bicester Bypass	Queen's Avenue opened in 1939 per the 1959 book "History of the County of Oxford". The 0.25 mile road between King's End and Field Street bypassed the town centre and was named Queen's Avenue in 1953 in commemoration of the Coronation. It later became unclassified.
1984	Kempston Southern Relief Road	The 1 mile single carriageway road from the new Marsh Leys Roundabout on Woburn Road to Ampthill Road was to be opened on 30 January 1984 by Allan Chapman, County Council Chairman (per the Biggleswade Chronicle of 27 January 1984). It later became part of the dualled Bedford Southern Bypass. Cost £2.92 million.
1986	Marston Moretaine Bypass	Opened on 16 December 1986 per the Noise Insulation Regulations notice. Became unclassified upon opening of the A421 Bedford to M1 J13 Ridgmont dual carriageway in 2010.
1996	Bedford Southern Bypass	Opened in 1996 per a Bedford Borough Council Report of July 2011. Work had started in August 1994 with a Summer 1996 completion scheduled. Contractor was a Wimpey / Amey joint venture, contract price £38 million.
1998	Finmere and Tingewick Bypass	Opened on 16 October 1998 by Bill Chapple, Chairman of Buckinghamshire County Council’s Environmental Services Committee. Cost £13.5 million.
2006	Great Barford Bypass	The 4.8 mile D2 dual carriageway from Bedford Bypass to A1 Black Cat Roundabout was officially opened on 24 August 2006. Design consultants: Capita Symonds/ Jacobs Babtie. Contractor was Edmund Nuttall, cost £57 million. Two emergency gates were fitted to allow access between the carriageways. The 17m long steel box gates had hidden wheels. Once lowered they allowed the gate to be pushed open. The main intended use was to allow stranded traffic to return on the opposite carriageway should the road ahead be blocked for a length of time.
2010	Bedford to M1 J13 Ridgmont	A second bypass for Marston Moretaine. The 8 mile dual carriageway opened on 1 December 2010. The existing Bedford Southern Bypass section between Marsh Leys and A6 was upgraded to D3, and M1 J13 Ridgmont was improved. Contractor was Balfour Beatty, outturn cost £154.6 million. The original Marston Moretaine bypass was retained as an unclassified road and converted to single carriageway.

Futures

The A421 is going to receive a new D2 expressway section between the Black Cat Roundabout and the Caxton Gibbet Roundabout to upgrade the existing S2 A428 as part of the A428 black cat to caxton gibbet scheme, which is due to be completed in 2026. The Black Cat Roundabout will be replaced with a 3 tier junction with the A1 with the A421 becoming a flyover, the A1 passing under a new roundabout, a new junction built to connect with the existing A428 and St Neots, and another junction with the A1198 to replace the Caxton gibbet roundabout.

Links

BBC News

• Milton Keynes A421: £28m road upgrade announced (22.03.2018)

gov.uk

• Oxford to Cambridge expressway strategic study: interim report (18 August 2016)

National Highways

• Highways England: Post Opening Project Evaluation - A421 Bedford to M1 J13 (5 Years After)  August 2017 (archive.org)

• A428 Black Cat to Caxton Gibbet