M40 motorway

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The M40 is a motorway connecting London and Birmingham. It provides an alternative route from the south to the Midlands, to the M1 and the A34.


The motorway is dual three lanes except for Junction 1A to J3, which is dual four lanes, a short section past J4, which is dual two lanes, and a short section past J9, two lanes southbound.

The motorway has four service areas:

  • Beaconsfield services (off J2), also accessible from the A355;
  • Oxford services (off J8A) also accessible from J8 and the A418;
  • Cherwell Valley services (off J10); and
  • Warwick services (between J12 and J13), consisting of two sites mirroring each other without a connection.

An Active Traffic Management system operates on the short section northbound from J16 (A3400) to the M42.


M40 at Burtley Wood, Buckinghamshire
M40 at Warmington, Warwickshire
The M40 heading westbound towards Junction 3 (High Wycombe)

The motorway between London and Oxford was constructed in stages between 1967 and 1974. The first section from the High Wycombe Bypass from Handycross to Stokenchurch (J4–5) opened in June 1967[1] with a temporary junction (J2*) opening in 1969, extending in a southerly direction to Holtspur just outside Beaconsfield. The 'Beaconsfield bypass' to J2 was built in 1971 and the 'Gerrards Cross Bypass' to J1 was completed in 1973. The section northbound from J5 to J8 (Pitmore to Chilworth Farm at Great Milton just outside Oxford) was completed in 1974.

At the design stage a service area was planned for Abbey Barns between Beaconsfield and High Wycombe, between J3 and J4, and the road has the beginnings of slip roads on both carriageways at this point.[2] The plans never reached fruition.[3]

Late in the 1960s, not long after the first stretch opened, the Ministry of Transport announced the possibility of building a motorway to link London with Birmingham as an alternative to the M1-M6 route – as well as improving road links to the South Coast ports for the Midlands – but it was not until 1983 that the decision to extend the M40 from Oxford to the south of Birmingham was made.

The preferred route was altered to avoid Otmoor after a vigorous road protest, which included selling over 3,000 small squares of a field to people all over the world. The field had been renamed 'Alice's field' as a reference to Alice in Wonderland by Lewis Carroll who lived in the area at the time he wrote the book.[4]

Construction began at Warwick in October 1987, with work on the section around Banbury starting in February 1988, and finally the section north of Oxford in July 1989. The section between the M42 and Warwick opened in December 1989, and the remainder in January 1991.[5]

It was planned that the section between J3A and the M5 would be renumbered as part of the M40, but this change did not take place.

By the time of the full opening, the original M40 had been widened, creating a dual three-lane motorway from start to finish.

The first service station opened as Cherwell Valley services in 1994 on the site of temporary toilet areas created when the motorway was constructed.[6]

The M40 had been expected to be the last major motorway, but in 1986 the Conservative government announced a major new road building scheme, Roads for Prosperity, much of which was cancelled in 1996 after major road protests.

Beginning in 1997, the motorway was widened to dual four lane between J1A and J3 (High Wycombe East) under a Private Finance Initiative. It was completed by a Carillion-John Laing joint venture in October 1998 – the original plan included widening between J3 and J4. Oxford services and Warwick Services opened in 1998.

Work to separate local and long distance traffic at J4 was completed in 2007, including a new dedicated left-turn slip lane between the A404 Marlow Bypass and the Oxford-bound M40; additional lanes on the slip roads entering the roundabout; an additional lane between the A404 Marlow Hill and the London-bound M40; and a five-lane cross link between the M40 and the A404(S).[7]

In 2009 the Highways Agency extended the Active Traffic Management (ATM) system onto the northbound carriageway from J16 to the junction with the M42. Beaconsfield services opened in 2009, near the site of the service station proposed at Abbey Barns almost 40 years earlier.

In August 2010 work started on J9, upgrading the southbound exit slip road to three lanes, and similar widening on the connecting A34 and A41 junctions. This was the first part of the work at this busy junction. If there is funding, a second part will commence, upgrading the northbound entrance and the A41 southbound entrance.[8]


Data[9] from driver location signs are used to provide distance and carriageway identifier information. Where a junction spans several hundred yards, both start and end locations are given.

M40 motorway
mile Southbound exits (B carriageway) Junction Northbound exits (A carriageway) Coordinates
18.1 End of motorway
Road continues as A40 to London
Start of motorway
Road formed from main carriageways of A40 from London
51°33’41"N, 0°29’45"W
Slough A412
Uxbridge A4020
Non motorway traffic
Watford (M1) Heathrow Airport (M4) (M3, M23, M11) M25 J1a Watford &(M1) Stansted Airport (M11) Heathrow Airport (M4)
Gatwick Airport (M23) M25
51°33’39"N, 0°31’53"W
Beaconsfield, Amersham, Slough A355, Beaconsfield services J2
Beaconsfield, Amersham, Slough A355, Beaconsfield services 51°35’39"N, 0°37’39"W
No access J3 Loudwater and High Wycombe (East) A40 51°36’12"N, 0°41’30"W
High Wycombe, Marlow, Maidenhead A404 (M4) J4 High Wycombe, Marlow A404 (M4) 51°36’44"N, 0°46’7"W
High Wycombe (West), Stokenchurch A40 J5 Stokenchurch A40 51°39’38"N, 0°54’46"W
Watlington, Princes Risborough B4009 J6 Thame, Watlington, Princes Risborough B4009 51°40’20"N, 0°57’38"W
No access J7 Thame, Wallingford, A329 51°43’28"N, 1°3’27"W
No access J8 Oxford, Cheltenham A40 51°43’56"N, 1°4’37"W
Thame, Aylesbury A418
Oxford (A40), Oxford services
Thame, Aylesbury A418
Oxford (A40), Oxford services
51°44’24"N, 1°5’44"W
Bicester, Aylesbury A41
Oxford, Newbury A34
J9 Bicester A41
Oxford, Newbury A34
51°52’8"N, 1°11’54"W
Northampton A43 (M1)
B430, Cherwell Valley services
Northampton A43 (M1)
B430, Cherwell Valley services
51°56’59"N, 1°12’22"W
Banbury A422
Daventry A361
J11 Banbury A422
Chipping Norton A361
52°4’22"N, 1°18’48"W
Gaydon B4451 J12 Gaydon B4451 52°11’32"N, 1°27’29"W
89.8 Warwick Services Services Warwick Services 52°13’5"N, 1°30’15"W
No access J13 Leamington, Warwick A452
52°14’26"N, 1°33’13"W
Leamington A452 J14 No access 52°15’25"N, 1°35’18"W
Warwick A429
Stratford, Coventry A46 Leicester (M69)
J15 Warwick A429
Stratford, Coventry A46 Leicester (M69)
52°15’36"N, 1°36’48"W
Henley A3400 J16 No access 52°20’6"N, 1°46’28"W
Start of motorway
Motorway is formed by two sliproads from the M42
(M42, J3a)
End of motorway
Road continues as M42
The SOUTH WEST, Birmingham (South & West), Redditch & M5
The North, Birmingham (North, East) (M1, M6)
52°20’51"N, 1°49’9"W
The path of the M40 corridor between London and Birmingham showing other important roads and major settlements.

Original M40

The M40 begins in Buckinghamshire at the Denham Roundabout near Uxbridge just east of the M25 and finishes in Warwickshire at the M42 near Birmingham. The A40 is a dual carriageway from the Inner Ring Road in Central London, and is one of the two busiest western radials. Much of the traffic using the A40 joins the M40. At J1 (the Denham Roundabout) outbound there is a lane drop to accommodate the non-motorway traffic. The A40 carries on to become the M40 with two lanes and a hard shoulder outbound, three lanes and a hard shoulder London bound. The motorway is carried over the top of the roundabout, which interchanges with the A40 (A413, A412) (outbound), the A4020 (original route of the A40) and the A412 southbound. The original line of the A40 can be seen going straight through the roundabout.

The motorway carries on for another half a mile before it reaches J1a, the free-flow interchange with the M25 London Orbital. It is a partially unrolled cloverleaf, with the smoothest turns from the London-bound M40 (from Oxfordshire, Warwickshire and the wider West Midlands) to the anti-clockwise M25 (London Heathrow, Gatwick, The Channel Ports) and vice versa, since this is the largest exchange of traffic between the two motorways. The M40 passes over the interchange, with the M25 on the bottom. The clockwise M25 enters the junction with four lanes with a lane drop to accommodate traffic heading for the M40 westbound, leaving the junction with three lanes. The anti-clockwise M25 enters the junction with three lanes, and gains a lane from the London-bound M40 to accommodate the extra traffic. The London-bound M40 enters with four lanes, with a lane drop for the M25 exit, leaves with three lanes, and the westbound M40 enters with lanes and gains a lane from the anti-clockwise M25.

After J1a the motorway is four lanes, and carries on for three miles until it reaches J2 for the A355 to Slough and the A40 to Beaconsfield and Gerrards Cross. J2 is a standard roundabout interchange, with the M40 underneath. Beaconsfield motorway services are just off the junction.

J3 is three miles further on, and serves the A40 for High Wycombe East and Loudwater. This is a restricted junction; the only flows are from the westbound M40 to the A40 and from the A40 to the London-bound M40. The westbound carriageway loses a lane, remaining three lanes for the rest of the route, and the London-bound carriageway gains a lane. The motorway then immediately crosses the valley (and Loudwater) over a large ramp-like bridge.

J4 is the interchange with the A404 – A404 north for High Wycombe and A404 south for Marlow, Maidenhead, Reading, Windsor and the M4. The motorway through the junction was not widened from the original two lanes when the rest of the motorway from J8 to London was, and so both carriageways experience a temporary lane drop. The junction used to be a straightforward roundabout interchange with exits for the M40 (west and east), High Wycombe (A404), the A4010, two local roads and the A404 dual carriageway to the south. During 2007, work was completed which included extra stacking space on the sliproads from the M40, provision for traffic from the A404 northbound to join the M40 westbound slip road without joining the roundabout and provision for the London-bound M40 to skip the section of the roundabout which serves the A4010, High Wycombe, and the A404 north.

The Stokenchurch Gap, "The Canyon" cutting in the Chiltern Hills.

The motorway enters Oxfordshire between J4 and J5, with the latter providing access to Stokenchurch, a basic diamond interchange and the fourth junction of the M40 with the A40. A mile farther on the motorway passes through a large cutting (the Stokenchurch Gap), known locally as "The Canyon" and reaches J6 with the B4009 for Lewknor, Watlington, and Chinnor. The junction is a variant on the diamond interchange, with the slip roads from the M40 south having sharp bends — upon leaving the M40 from the westbound carriageway there is an immediate turn of almost 90° to the left and shortly after a sharp 90° turn to the right before a junction with the B4009, and similarly when entering the London-bound M40.

On its completion in 1967, the M40 finished at junction 5. The route was expanded a few years later to reach junction 7 and come within a few miles of Oxford. It was designated as a motorway to link London with one of the country's leading university cities. A similar scenario explained the construction of the M11 motorway linking London with Cambridge a few years later.[10]

Just over a mile after junction 6 the motorway passes to within 100 yards of St Giles Church, Tetsworth and two miles farther on meets the first of three junctions in close succession. Junction 7 is a restricted junction with the A329 serving Thame and the A40. Access is limited allowing exit for only northbound traffic and entry only for southbound traffic. The exiting slip road on the southbound M40 at J7 is for "Works Traffic Only" to a depot. A slip road exists to allow traffic from the A329 to join the M40 north but is closed to traffic by a gate: this traffic must therefore follow the A40 to Junction 8, two miles to the north.

Connection between old and new mainline of M40

At Junction 8 a spur off the M40 with two-lane carriageways leaves the mainline of the motorway and continues for a few miles before ending at a trumpet junction for Wheatley and the A418 (A40) (the old junction 8), with the road continuing as a two lane dual carriageway as the A40 towards Oxford and farther on to Cheltenham and eventually Fishguard in Pembrokeshire. The spur can be accessed only via the M40 northbound, and traffic heading towards the M40 can join only the southbound carriageway. This short spur is the end of the original M40, prior to the building of the current Junction 8 and extension to Birmingham.

After Junction 8, the M40 – the mainline – begins to head north and in less than a mile, reaches Junction 8A, for the A418, east to Thame and Aylesbury, as well as the single-carriageway A40, south to London. It also serves Wheatley, via the A418 (A40) via the dumbbell junction with the M40 spur. The junction allows traffic from the southbound M40 to enter Oxford, via the A40 dual-carriageway, and traffic from the A40 from Oxford to enter the northbound M40, via the linking road. The Oxford Services are also located on J8A, making the motorway accessible from the M40, A40 (Oxford), A418, A40 (London) and the A329. Leaving J8A, the M40 north has a sharp northerly turn, and prior to the extension of the motorway opening, local police patrol cars were used to check the turn could be safely navigated at and above the national speed limit, such was the abrupt change of direction.

"The Missing Link"

The road travels for 12 miles, briefly re-entering Buckinghamshire, before reaching junction 9 for the A34 and A41. The A34 dual carriageway serves Oxford and is a trunk route for Newbury, Winchester and Southampton (via the M3) as well as the rest of the south coast.. The A41 dual carriageway serves Bicester and Aylesbury, and both roads meet the motorway at Wendelbury roundabout junction. This junction design is very inefficient and cannot cope with a very large volume of traffic using the junction. To try to alleviate this problem, there is a temporary lane drop for the London-bound carriageway. The largest exchange of traffic is between the A34 and the M40 north, and traffic on those roads backs up and causes congestion on both roads (going north and south), as well as on the interchange itself. North of the junction, the existing A34 becomes the A3400. This means the A34 is now technically in two halves (it regains status farther up the road at J16, although signs on the motorway do not mention this). Instead, the first signs for the A34 from a motorway are on the M42 at J4, as with the A41.

The M40 follows a course of almost due north for five miles before reaching Junction 10, for the Cherwell Valley services, the A43 and the village of Ardley. The A43 terminates at J10, although originally it carried on to Kidlington, the southern part of the old route now used by the re-routed A34. The A43 serves Brackley, Silverstone and its racing circuit, home to the British Grand Prix. Farther on, the A43 leads to Northampton and the M1. Junction 10 was originally a dumbbell junction. The capacity of both the junction and the single carriageway A43 proved too small when the road was used as a freight thoroughfare from the congested M1 to the M40 to London, and the A34 at J9 to the south coast — in fact the five-mile stretch between these junctions is the busiest on the motorway in both directions. When the A43 (between the M1 and M40) was upgraded to dual carriageway, the junction was redesigned and rebuilt by the Highways Agency to cope with the extra traffic. A third roundabout was added to the junction, to the north, with the slips for the southbound M40 and the A43, with the slip roads for the northbound M40 remodelled as well, and the roundabout in the middle now serving the services.

The slip road for the London-bound carriageway which used to be accessed from the roundabout is now reached only via the services. The design and execution of the revised design of new junction is greatly derided, mostly because of the three roundabouts giving no priority to the main flow of traffic, (A43-M40 London), and the slip roads off and onto the motorway (except the one accessed via the services) have sharp turns and adverse cambers, which results lorries frequently tipping over and spilling their loads especially on the roundabout at the end of the northern carriageway. The junction fails to perform its function as an effective traffic junction. As well, the slip roads onto the motorway give little manoeuvring space as both join the motorway under (the same) bridge built for the old junction.[11]

The motorway then follows a winding route north for 10 miles, passing into Northamptonshire twice until Junction 11, the A422 and A361, serving Banbury. The motorway does not follow the straight route to the east of Middleton Cheney, meeting with the A422, as it had once been planned, due to a major landowner refusing his land to be cut in two. If built as planned, J11 would be east of Middleton Cheney, meeting with the A422, and probably would have fuelled major growth in the village as well as Banbury, the primary destination of the junction. As it is, the junction was built a mile and a half west along the A422, with the motorway skirting Banbury. The junction itself is a regular roundabout interchange, and has the single carriageway A361 from Daventry the dual-carriageway A422 from Brackley and the A43 from the west, and the dual-carriageway A422 (A361) toward Banbury feeding to/from it.

After re-entering Oxfordshire north of Banbury the motorway then enters Warwickshire before reaching Junction 12, some 12 miles north-west of J11. J12 servse Gaydon and the Heritage Motor Centre via the B4451. The junction is a standard diamond interchange. Farther along the motorway is Warwick Services, the last on the motorway, before it reaches the restricted access Junction 13. This serves Leamington Spa and Warwick via the A452, and Gaydon via the B4100. The junction is incomplete as a half-diamond interchange, with access only from the northbound carriageway and access to the southbound M40.

The junction is completed two miles farther on at Junction 14, another restricted access junction, with access to the A452 from the southbound M40, and the access on to the motorway is in a northbound direction. The slip roads join at a roundabout and carry on as the single carriageway A452 to meet with the A452 to Leamington Spa, A425 to Warwick, and the A452 to J13. A few hundred yards further up is junction 15, known as Longbridge island. This is a large, regular roundabout interchange, and is always busy during peak times due to the various destinations it serves, including The Cotswolds, Stratford-upon-Avon, Coventry, and Warwick. Farther north, Henley-in-Arden (J16) is again 'incomplete' to discourage local traffic.

The motorway joins the M42 in both directions, with northbound traffic taking the left lane to exit eastbound, eventually forming the outer lanes of the M42 via a tight-bending two lane connecting road, and the right lanes being taken eastbound. Similarly, southbound, eastbound traffic from the M42 splits off from the outer two lanes, whereas westbound traffic of the M42 has a single lane, widening to a two lane slip road, which merges with the middle lane and forms the outer lane of the southbound M40.


Outside links

("Wikimedia Commons" has material
about M40 motorway)
Motorways in the United Kingdom

Great Britain: M1  • M2  • M3  • M4  • M5  • M6  • M6 Toll  • M8  • M9  • M10  • M11  • M18  • M20  • M23  • M25  • M26  • M27  • M32  • M40  • M42  • M45  • M48  • M49  • M50  • M53  • M54  • M55  • M56  • M57  • M58  • M60  • M61  • M62  • M63  • M65  • M66  • M67  • M69  • M73  • M74  • M77  • M80  • M85  • M90  • M180  • M181  • M271  • M275  • M602  • M606  • M621  • M876  • M898  • Sections of A road: A1(M)

Former motorways marked in italics

Northern Ireland: M1  • M2  • M3  • M5  • M12  • M22