This is the London end of the M40, from Denham at Junction 1, through the M25 interchange at Junction 1A and past Beaconsfield, to the Handy Cross junction at High Wycombe. Reports for this stretch are shown below.

The junctions on this stretch

• Junction 1 — the A40, A412 and A4020 for Denham and Uxbridge. The M40 begins here as the A40 from London becomes motorway.
• Junction 1A — the M25 for Heathrow, Watford and the M1. This is M25 Junction 16.
• Junction 2 — the A355 for Beaconsfield, Amersham and Slough, and Beaconsfield services.
• Junction 3 — the A40 for the east side of High Wycombe and Loudwater.
• Junction 4 — the A404 at Handy Cross for High Wycombe, Marlow, Maidenhead and the M4.

How busy is this stretch?

This is the busiest part of the M40. The Department for Transport’s 2025 counts are:

Stretch	All vehicles	Lorries	Share lorries
J1 to J1A	94,888	5,976	6.3%
J1A to J2	136,403	8,242	6.0%
J2 to J3	133,167	7,496	5.6%
J3 to J4	102,154	6,656	6.5%

Junction 1A to 2 is the busiest count point on the whole motorway. Across the M25 junction the figure drops by about 30%, to 94,888 between Junctions 1 and 1A. At Junction 1 the DfT also counts 78,017 vehicles a day on the A40/A412 link.

Which way the traffic runs

Split by direction, the stretch from Denham to the M25 is the most uneven at this end of the road: 53,303 vehicles a day heading away from London against 41,585 heading in. Between the M25 and Beaconsfield the split is close to even, 66,843 northbound and 69,560 southbound. See northbound and southbound traffic for every stretch.

Links to other motorways

For the orbital, see M25 Traffic. For the M4 via the A404 at Junction 4, see M4 Traffic.

Next stretch: Junctions 4 to 7, Stokenchurch and the Chilterns. All stretches: M40 maps.

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