Motorway
A404(M) traffic and collisions
The A404(M) is a motorway of 2.5 miles, in Windsor and Maidenhead. This page covers its traffic at 3 DfT count points since 2016 and the collisions police recorded on it.
- Traffic in 2025 54m vehicle miles
- Average daily traffic 58,950 vehicles a day, both directions
- Busiest section 65,651 M4 to J9A
- HGV share 3.5% of vehicle miles
- Traffic since 2019 +6.9% same count points
How busy is the A404(M)?
On an average day in 2025, 58,950 vehicles passed each point on the A404(M), counting both directions. The busiest section is M4 to J9A (Windsor and Maidenhead), with 65,651 a day; the quietest listed is J9A to J9B, with 57,783.
Busiest sections, 2025
M4 to J9A carries 1.1 times the road’s average flow.
| Section | Vehicles a day |
|---|---|
| M4 to J9A Windsor and Maidenhead · 0.8 mi · HGVs 3.2% | 65,651 |
| J9A to J9B Windsor and Maidenhead · 1.5 mi · HGVs 3.7% | 57,783 |
Source:DfT,UK Motoring analysis 2016 to 2025 Updated
Route
In Windsor and Maidenhead · 2.5 miles
A404(M) traffic and collisions by section
3 sections between junctions, in route order. Each is the average of its DfT count points, weighted by length.
Sections Tap a column heading to sort
| # | |||
|---|---|---|---|
| 1 | M4 to J9AWindsor and Maidenhead | 65,651 | – |
| 2 | J9A to J9BWindsor and Maidenhead | 57,783 | – |
| 3 | A4 to A404Windsor and Maidenhead | 40,903 | – |
Vehicles a day is the average daily flow in 2025. “Since 2019” compares the same count points. Collisions are those with the A404(M) as the first road, placed on the nearest section by their recorded position; rates (per 100 million vehicle miles) are shown for sections of half a mile or more with 10 or more.
A404(M) traffic by vehicle type
Cars and taxis make up 80.9% of the vehicle miles on the A404(M). HGVs account for 3.5%.
Vehicle mix, 2025
Source:DfT,UK Motoring analysis 2016 to 2025 Updated
HGV share of traffic
| Year | HGV share |
|---|---|
| 2016 | 4.7% |
| 2017 | 5.2% |
| 2018 | 4.9% |
| 2019 | 5.1% |
| 2020 | 6.6% |
| 2021 | 6.3% |
| 2022 | 5.7% |
| 2023 | 5.5% |
| 2024 | 4.2% |
| 2025 | 3.5% |
Source:DfT,UK Motoring analysis 2016 to 2025 Updated
A404(M) traffic trend
Traffic on the A404(M) came to 53.8 million vehicle miles in 2025. At the count points present in both years, it is up 6.9% on 2019, before the pandemic.
Vehicle miles a year
| Year | Vehicle miles |
|---|---|
| 2016 | 19m |
| 2017 | 52m |
| 2018 | 50m |
| 2019 | 50m |
| 2020 | 31m |
| 2021 | 33m |
| 2022 | 38m |
| 2023 | 39m |
| 2024 | 48m |
| 2025 | 54m |
Source:DfT,UK Motoring analysis 2016 to 2025 Updated
Average daily flow
| Year | Vehicles a day |
|---|---|
| 2016 | 64,356 |
| 2017 | 57,013 |
| 2018 | 54,953 |
| 2019 | 55,144 |
| 2020 | 33,517 |
| 2021 | 36,440 |
| 2022 | 41,685 |
| 2023 | 42,763 |
| 2024 | 52,306 |
| 2025 | 58,950 |
Source:DfT,UK Motoring analysis 2016 to 2025 Updated
The chart counts the whole road as it was each year, so new or renumbered stretches move it. The percentage changes compare only count points present in both years. In 2025, 1 of the 3 count points were counted; DfT estimated the rest from earlier counts and local trends.
A404(M) collisions
Police recorded fewer than 3 collisions with the A404(M) as the first road from 2021 to 2025, fewer than 3 of them fatal or serious.
Reported collisions by year
| Year | Collisions | Fatal or serious |
|---|---|---|
| 2021 | 7 | fewer than 3 |
| 2022 | 0 | 0 |
| 2023 | 5 | fewer than 3 |
| 2024 | fewer than 3 | 0 |
| 2025 | fewer than 3 | 0 |
Source:DfT STATS19,UK Motoring analysis 2021 to 2025 Updated
A further 9 collisions were recorded at junctions where the A404(M) was the second road; they are not in the figures above. Fatal or serious uses DfT’s adjusted serious figures. How we count collisions
Council areas on the A404(M)
In route order. Each is the highway authority DfT files the count points under.
- Windsor and Maidenhead
Planned closures on the A404(M) in England
National Highways has 4 planned closures on the A404(M) between 16 September 2026 and 30 September 2026, all of them starting in that period. 3 close a carriageway rather than a lane or slip road, and 4 start between 7pm and 6am.
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Carriageway A404M northbound Jct 9b exit slip road closure
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Carriageway A404M southbound Jct 9b entry slip road closure
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Carriageway A404M southbound Jct 9b exit slip road closure
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Lane or slip A404 southbound lane 1 closure (50/8 to 48/1)
Planned closures only: National Highways can cancel or change them, and closures caused by incidents are not shown. Council roads in England are not covered. Roadworks and closures across the UK
Source:National Highways 2026-09-16 to 2026-09-30 Updated
Data sources and methodology
| Figures | Source | Period | Records | Updated |
|---|---|---|---|---|
| Traffic counts and vehicle mix | Road traffic statistics (AADF by count point) Department for Transport Derived statistics UK Motoring | 2016 to 2025 | 3 count points in 2025 | 15 September 2026 |
| Reported collisions | Road safety open data (STATS19) Department for Transport Derived statistics UK Motoring | 2021 to 2025 | 14 reported collisions | 15 September 2026 |
| Planned closures | Transport Data Feeds (DATEX II) National Highways | 2026-09-16 to 2026-09-30 | 2,304 planned closure schemes | 16 September 2026 |
- Annual average daily flow (AADF) is the average number of vehicles passing a point on a typical day of the year, both directions combined.
- Vehicle miles are AADF multiplied by link length and 365, summed over every count point link on the road.
- Sections join count point links between junctions, using the link lines in DfT’s major road database.
- STATS19 covers personal injury collisions reported to the police. Damage-only collisions are not included, and not every injury collision is reported.
- Serious and slight figures are DfT’s adjusted estimates, which allow for police forces moving to injury-based reporting.
- Counts of one or two collisions below Great Britain level are shown as “fewer than 3”.
Contains public sector information licensed under the Open Government Licence v3.0.
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