Southbound on the M40 is the London-bound carriageway: from the M42 south of Birmingham, down past Warwick, Banbury and Oxford, over the Chilterns and into the M25 and Denham. This page shows reports affecting that direction.

The run into London

Joining from the M42 at Junction 3A, southbound traffic passes Henley-in-Arden, Warwick and Leamington before the long rural section through north Oxfordshire. At Junction 8 the road swings east with the A40 joining from Oxford, then passes through the Stokenchurch Gap in the Chilterns towards High Wycombe.

The traffic builds sharply at the London end. The last two stretches before the M25 are the busiest on the whole southbound carriageway.

Southbound traffic, stretch by stretch

These are the Department for Transport’s 2025 daily counts for traffic heading towards London only, listed in the order you drive them.

Stretch	All vehicles	Cars & taxis	Lorries
M42 J3A to J16	46,865	35,440	3,855
J16 to J15 Warwick	47,305	34,503	5,041
J15 to J14	54,648	41,827	4,593
J14 to J13 Leamington	42,552	32,767	3,730
J13 to J12 Gaydon	42,393	31,864	4,729
J12 to J11 Banbury	45,146	32,903	5,472
J11 to J10 Cherwell Valley	42,393	31,443	3,961
J10 to J9 Bicester	44,262	32,969	4,780
J9 to J8 Oxford	30,917	23,809	2,103
J8 to J7 Thame	45,744	35,738	3,127
J7 to J6 Lewknor	48,487	37,823	3,219
J6 to J5 Stokenchurch	50,520	39,321	4,027
J5 to J4 High Wycombe	50,895	38,193	3,179
J4 to J3	50,805	39,403	3,245
J3 to J2 Beaconsfield	68,532	53,346	3,756
J2 to J1A (M25)	69,560	53,995	3,818
J1A to J1 Denham	41,585	30,827	2,778

Southbound traffic peaks between Junction 2 and Junction 1A, at 69,560 vehicles a day — a little more than the northbound peak on the same stretch. It then falls to 41,585 between the M25 and Denham, once past the orbital. The quietest southbound stretch is Junction 9 to 8 on the Oxford side, at 30,917.

The Department for Transport labels most M40 count points eastbound and westbound, and the stretch from Oxford to Banbury northbound and southbound, because the road changes bearing. We read westbound and northbound as travel away from London, and eastbound and southbound as travel towards London. That is our reading of the compass letters, not a label the dataset gives. Where one stretch has more than one count point we show one; between Junctions 8 and 9 we use the count point labelled north and south.

Where to stop southbound

Warwick has a separate southbound site, and the other three — Cherwell Valley, Oxford and Beaconsfield — are at junctions, so they serve both directions. See Warwick services.

If you are continuing onto the orbital at Junction 1A, check M25 Traffic before you reach it.

Heading the other way? M40 northbound traffic towards Birmingham

Traffic count figures on this page are from the Department for Transport road traffic statistics, 2025.