How busy the M3 really is, stretch by stretch, using the Department for Transport’s own road traffic counts. These are not our estimates and they are not modelled — they are the official 2025 figures, and we show you which ones were physically counted and which the Department itself marked as estimated.

The headline

The M3 runs 58.6 miles (94.3 km) from Junction 1 at Sunbury to Junction 14 at the M27. Along it the Department for Transport measures 15 stretches of mainline, and the difference between the busiest and the quietest is bigger than most people expect.

M3 Traffic Statistics: the key numbers

Measure	Figure	Where
Busiest stretch	140,750 vehicles a day	J13 Chilworth to J14 (M27)
Quietest mainline stretch	56,135 vehicles a day	J9 Winchester to J8 A303
Most lorries	11,545 a day	J10 Chilcomb to J11 Compton
Highest lorry share	9.4% of all traffic	J9 Winchester to J10 Chilcomb
Biggest difference in traffic between the two directions	26% more westbound than eastbound	J4A Fleet to J4 Frimley
Most even split of traffic between the two directions	0.8% difference	J10 Chilcomb to J11 Compton

© M3Traffic.co.uk · Statistics from the Department for Transport

Put plainly: the M3 carries two and a half times more traffic at its Southampton end than it does across the middle of Hampshire, and it almost doubles in a single junction where the A34 joins at Winchester.

Every measured stretch of the M3, busiest first

All 15 mainline stretches, 2025 figures. Stretches marked est. are the Department for Transport’s own estimate rather than a physical count — we publish them, and we label them.

Every measured stretch of the M3, busiest first

Stretch	Miles	Vehicles per day	Lorries	Lorry share
J13 Chilworth to J14 (M27)	1.2	140,750	9,901	7.0%
J12 Eastleigh to J13 Chilworth	1.7	130,785	9,893	7.6%
J11 Compton to J12 Eastleigh	3.5	128,023	9,384	7.3%
J10 Chilcomb to J11 Compton	0.8	126,217	11,545	9.1%
J3 Lightwater to Kitsmead Lane flyover	5.5	123,417	8,271	6.7%
J4 Frimley to J3 Lightwater	4.5	118,589	6,774	5.7%
Kitsmead Lane flyover to the M25 (J2)	2.1	113,905	7,713	6.8%
J9 Winchester to J10 Chilcomb	1.4	110,741	10,404	9.4%
J6 Basingstoke to J5 Hook	4.8	103,624	5,892	5.7%
J8 A303 to J7 Basingstoke (est.)	1.2	101,834	5,995	5.9%
J5 Hook to J4A Fleet	7.5	96,243	5,578	5.8%
J7 to J6 Basingstoke (est.)	4.9	94,624	5,972	6.3%
J4A Fleet to J4 Frimley	2.1	93,372	5,104	5.5%
J2 (M25) to J1 Sunbury (est.)	5.8	62,848	1,892	3.0%
J9 Winchester to J8 A303	11.0	56,135	3,515	6.3%

© M3Traffic.co.uk · Statistics from the Department for Transport

Traffic news for the busiest junctions

• J12 to J14 — Eastleigh, Chilworth & the M27 — the busiest part of the motorway
• J10 Chilcomb — more lorries than anywhere else on the M3
• J9 A34 Winchester — where the traffic almost doubles
• J3 Lightwater — the busiest counted stretch in Surrey
• J2 — the M25 interchange — where about 45% of the traffic changes motorway
• J4 & J4A Farnborough — the most one-sided stretch of the M3

What these numbers are, and what they are not

They are annual average daily flows: total traffic over a year, divided by 365. That makes them excellent for comparing one stretch of road with another, and useless for telling you what Tuesday at half past five looks like. A stretch averaging 140,750 vehicles a day is carrying far more than that at peak and far less at four in the morning.

They are also last year’s figures. For what is happening on the M3 right now, use the live M3 traffic news — and bear in mind that no traffic feed, ours included, ever has the complete picture of a motorway.