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Trunk A-road

A404 traffic and collisions

The A404 is a trunk A-road of 42.6 miles, from Westminster to Windsor and Maidenhead. This page covers its traffic at 48 DfT count points since 2000 and the collisions police recorded on it.

Last updated
Records analysed
48 count points in 2025
Methodology
View methodology
  • Traffic in 2025 368m vehicle miles
  • Average daily traffic 23,675 vehicles a day, both directions
  • Busiest section 56,402 A4155 to A308
  • HGV share 2.7% of vehicle miles
  • Traffic since 2019 −2.7% same count points
  • Collisions, 2021 to 2025 1,289 73.2 per 100m vehicle miles

How busy is the A404?

On an average day in 2025, 23,675 vehicles passed each point on the A404, counting both directions. The busiest section is A4155 to A308 (Buckinghamshire, Windsor and Maidenhead), with 56,402 a day; the quietest listed is Headstone Lane to A410, with 10,414.

Busiest sections, 2025

A4155 to A308 carries 2.4 times the road’s average flow.

Sections of the A404 with the highest average daily flow, 2025
Section Vehicles a day
A4155 to A308 Buckinghamshire, Windsor and Maidenhead · 2.2 mi · HGVs 3.3% 56,402
M40 to A4155 Buckinghamshire · 2.2 mi · HGVs 3.9% 55,357
Hurley Lane to A4130 Windsor and Maidenhead · 1.9 mi · HGVs 3.6% 53,554
A4130 to A404M Windsor and Maidenhead · 0.9 mi · HGVs 3.5% 51,129
At A4130 Windsor and Maidenhead · 0.7 mi · HGVs 3.5% 39,881
A404 intersection to M40 Buckinghamshire · 1.3 mi · HGVs 1.3% 31,995
A4127 to A409 Brent · 0.9 mi · HGVs 1.6% 29,044
A4145 to A412 Hertfordshire · 0.7 mi · HGVs 1.9% 28,528
A407 to A406 Brent · 0.9 mi · HGVs 4.3% 20,976
A410 to Elm Park Rd Harrow · 0.8 mi · HGVs 1.4% 20,508

Source:DfT,UK Motoring analysis 2000 to 2025 Updated

Route

Westminster to Windsor and Maidenhead · 42.6 miles

Westminster Windsor and Maidenhead
Schematic route: each line joins the junctions at the ends of a DfT count point link.

A404 traffic and collisions by section

41 sections between junctions, in route order. Each is the average of its DfT count points, weighted by length. 2 short link roads and spurs (0.4 miles) count in the road’s totals but are not listed.

Show all 41 sections Tap a column heading to sort
Sections of the A404 in route order, 2025 traffic
#
1A40 to A4207Westminster1.313,5441.8%−20.2%171494.2
2A4207 to A219Westminster, Brent1.813,2282.5%−14.8%146345.4
3A219 to Tubbs RoadBrent0.216,2583.5%−27.1%21–
4Tubbs Road to A404 Manor Park RoadBrent0.210,9187.2%−11.6%54–
5A404 Craven Park Road to Intersection with Park Parade (minor road) and A404 Station RoadBrent0.512,1915.0%–39873.3
6A404 split to A407Brent0.214,8743.2%+12.6%44–
7A407 to A406Brent0.920,9764.3%+4.3%85247.0
8A406 to A4179Brent0.919,4462.7%−4.7%89284.4
9A4179 to A4089Brent0.312,5701.5%−17.7%41–
10At A4089Brent0.318,5911.8%+9.1%60–
11A4089 to A4005Brent0.717,0371.0%−2.1%47233.3
12At A4005Brent0.425,0411.0%+6.2%34–
13A4005 to A4088Brent0.416,6452.9%+22.4%12–
14A4088 to A4127Brent0.422,4432.7%+27.2%15–
15A4127 to A409Brent0.929,0441.6%−12.3%4492.6
16A409/A4006 roundabout to B458Harrow0.425,6381.1%+3.1%22–
17B458 to A312Harrow0.426,6102.1%−9.4%16–
18A312 to A4005Harrow0.132,0211.6%−8.7%3–
19A4005 to A4090Harrow0.913,8731.7%−9.0%2194.5
20A4090 to Headstone LaneHarrow0.415,7051.7%−15.1%10–
21Headstone Lane to A410Harrow1.210,4142.6%+7.1%2087.4
22A410 to Elm Park RdHarrow0.820,5081.4%−13.9%1550.1
23Elm Park Rd to A4125Harrow, Hillingdon1.319,4301.6%−20.9%4290.9
24A4125 to A4180Hillingdon1.215,9530.8%−2.1%1237.2
25A4180 to A4145Hillingdon, Hertfordshire2.017,9081.9%−10.9%1523.6
26A4145 to A412Hertfordshire0.728,5281.9%+4.3%1337.9
27A412 to M25Hertfordshire1.616,8592.4%−9.1%1225.2
28M25 to road from North Hill, ChorleywoodHertfordshire1.018,8332.9%−9.1%9–
29road from North Hill to Church Grove, Little ChalfontHertfordshire, Buckinghamshire2.015,5182.8%+6.2%fewer than 3–
30Church Grove, Little Chalfont to A404 Woodside Road roundaboutBuckinghamshire1.713,5021.7%−5.3%1536.9
31A404 Woodside Road roundabout to A355Buckinghamshire0.914,1572.4%−19.9%3–
32Inkerman Drive to A413Buckinghamshire3.813,5201.9%−0.1%1719.1
33B474 to Inkerman Drive, HazelmereBuckinghamshire2.912,9221.0%+1.3%3352.9
34A404 to A404 intersectionBuckinghamshire0.110,9701.2%−6.3%fewer than 3–
35A404 intersection to M40Buckinghamshire1.331,9951.3%−13.8%3444.8
36M40 to A4155Buckinghamshire2.255,3573.9%+9.2%2512.2
37A4155 to A308Buckinghamshire, Windsor and Maidenhead2.256,4023.3%+3.5%115.2
38Hurley Lane to A4130Windsor and Maidenhead1.953,5543.6%−0.6%8–
39At A4130Windsor and Maidenhead0.739,8813.5%+0.4%fewer than 3–
40A4130 to A404MWindsor and Maidenhead0.951,1293.5%−3.2%fewer than 3–
41A404M to A4Windsor and Maidenhead0.210,2263.5%−3.2%0–

Vehicles a day is the average daily flow in 2025. “Since 2019” compares the same count points. Collisions are those with the A404 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 traffic by vehicle type

Cars and taxis make up 80.1% of the vehicle miles on the A404. HGVs account for 2.7%, rising to 5.0% on A404 Craven Park Road to Intersection with Park Parade (minor road) and A404 Station Road.

Vehicle mix, 2025

Source:DfT,UK Motoring analysis 2000 to 2025 Updated

HGV share of traffic

HGVs as a share of vehicle miles on the A404, by year
Year HGV share
2000 3.5%
2001 3.3%
2002 3.4%
2003 3.3%
2004 3.4%
2005 3.3%
2006 3.3%
2007 3.3%
2008 3.2%
2009 3.5%
2010 3.6%
2011 3.0%
2012 3.2%
2013 3.3%
2014 3.3%
2015 3.6%
2016 3.5%
2017 3.2%
2018 3.1%
2019 2.9%
2020 3.5%
2021 3.6%
2022 3.5%
2023 3.1%
2024 2.8%
2025 2.7%

Source:DfT,UK Motoring analysis 2000 to 2025 Updated

A404 traffic trend

Traffic on the A404 came to 368 million vehicle miles in 2025. At the count points present in both years, it is down 2.7% on 2019, before the pandemic, and down 3.0% on 2015.

Vehicle miles a year

Like for like, traffic is down 9.6% on 2000.

Vehicle miles on the A404 each year, the whole road as it was that year
Year Vehicle miles
2000 429m
2001 427m
2002 434m
2003 432m
2004 434m
2005 443m
2006 434m
2007 426m
2008 425m
2009 418m
2010 423m
2011 424m
2012 417m
2013 405m
2014 418m
2015 424m
2016 416m
2017 386m
2018 389m
2019 378m
2020 274m
2021 316m
2022 355m
2023 359m
2024 364m
2025 368m

Source:DfT,UK Motoring analysis 2000 to 2025 Updated

Average daily flow

Average daily flow along the A404, weighted by link length, by year
Year Vehicles a day
2000 26,910
2001 26,765
2002 27,213
2003 27,096
2004 27,236
2005 27,705
2006 27,190
2007 26,690
2008 26,517
2009 26,103
2010 26,369
2011 26,474
2012 26,044
2013 25,254
2014 25,817
2015 26,210
2016 26,188
2017 25,132
2018 24,913
2019 24,324
2020 17,596
2021 20,291
2022 22,802
2023 23,112
2024 23,375
2025 23,675

Source:DfT,UK Motoring analysis 2000 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, 13 of the 48 count points were counted; DfT estimated the rest from earlier counts and local trends.

A404 collisions

Police recorded 1,289 collisions with the A404 as the first road from 2021 to 2025, 216 of them fatal or serious, including 9 fatal. That is 73.2 per 100 million vehicle miles, higher than the 31.5 for all A-roads in Great Britain. On average there were 6.1 a year for each mile of road.

Reported collisions by year

Up 2.9% from 2021 to 2025.

Police-reported collisions on the A404 by year: fatal or serious, and slight
Year SlightFatal or serious
2021 21030
2022 25552
2023 21045
2024 19941
2025 19948

Source:DfT STATS19,UK Motoring analysis 2021 to 2025 Updated

Sections with the highest collision rates

Per 100 million vehicle miles, 2021 to 2025. Sections of half a mile or more with 10 or more collisions.

Collisions per 100 million vehicle miles by section of the A404, 2021 to 2025
Section Per 100m vehicle miles
A404 Craven Park Road to Intersection with Park Parade (minor road) and A404 Station Road Brent · 39 collisions 873.3
A40 to A4207 Westminster · 171 collisions 494.2
A4207 to A219 Westminster, Brent · 146 collisions 345.4
A406 to A4179 Brent · 89 collisions 284.4
A407 to A406 Brent · 85 collisions 247.0
A4089 to A4005 Brent · 47 collisions 233.3
A4005 to A4090 Harrow · 21 collisions 94.5
A4127 to A409 Brent · 44 collisions 92.6

Source:DfT STATS19,UK Motoring analysis 2021 to 2025 Updated

A further 153 collisions were recorded at junctions where the A404 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

In route order. Each is the highway authority DfT files the count points under.

  • Westminster
  • Brent
  • Harrow
  • Hillingdon
  • Hertfordshire
  • Buckinghamshire
  • Windsor and Maidenhead

Planned closures on the A404 in England

National Highways has 10 planned closures on the A404 between 16 September 2026 and 30 September 2026, all of them starting in that period. 2 close a carriageway rather than a lane or slip road, and 10 start between 7pm and 6am.

  • Carriageway A404M northbound Burchetts Green exit slip road closure

    16 Sept 21:00 to 17 Sept 06:00 Road maintenance

  • Carriageway A404M northbound Burchetts Green entry slip road closure

    16 Sept 21:00 to 17 Sept 06:00 Road maintenance

  • Lane or slip A404 northbound lane 1 closure (50/9 to 53/8)

    17 Sept 20:30 to 18 Sept 06:00 Road maintenance

  • Lane or slip M40 Southbound Jct 5 to Jct 4 lane 3 and lane 2 closure

    21 Sept 21:00 to 24 Sept 06:00 Road maintenance Also affects M40

  • Lane or slip M40 Jct 4 roundabout lane 1 closure

    22 Sept 21:00 to 23 Sept 06:00 1 of 4 lanes Road maintenance

  • Lane or slip A404 southbound lane 1 closure (50/8 to 48/1)

    22 Sept 21:00 to 23 Sept 06:00 1 of 2 lanes Road maintenance Also affects A404(M)

  • Lane or slip M40 Jct 4 roundabout lane 1 closure

    23 Sept 21:00 to 24 Sept 06:00 1 of 4 lanes Road maintenance

  • Lane or slip A404 northbound lane 2 closure (53/0 to 53/8)

    28 Sept 20:00 to 29 Sept 06:00 Road maintenance

2 more planned closures in this period are not shown.

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

Datasets used on this page
Figures Source Period Records Updated
Traffic counts and vehicle mix Road traffic statistics (AADF by count point) Department for Transport
Derived statistics UK Motoring 		2000 to 2025 48 count points in 2025 15 September 2026
Reported collisions Road safety open data (STATS19) Department for Transport
Derived statistics UK Motoring 		2021 to 2025 1,289 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”.
How we calculate these figures All data sources

Contains public sector information licensed under the Open Government Licence v3.0.

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