A-road
A400 traffic and collisions
The A400 is an A-road of 6.3 miles, from Camden to Islington. This page covers its traffic at 19 DfT count points since 2000 and the collisions police recorded on it.
- Traffic in 2025 25m vehicle miles
- Average daily traffic 10,958 vehicles a day, both directions
- Busiest section 17,240 A501 to Harrington Sq
- HGV share 3.7% of vehicle miles
- Traffic since 2019 −15.1% same count points
- Collisions, 2021 to 2025 511 404.0 per 100m vehicle miles
How busy is the A400?
On an average day in 2025, 10,958 vehicles passed each point on the A400, counting both directions. The busiest section is A501 to Harrington Sq (Camden), with 17,240 a day; the quietest listed is A501 to New Oxford St, with 8,058.
Busiest sections, 2025
A501 to Harrington Sq carries 1.6 times the road’s average flow.
| Section | Vehicles a day |
|---|---|
| A501 to Harrington Sq Camden · 0.6 mi · HGVs 3.2% | 17,240 |
| Royal College St to A5200 Camden · 0.9 mi · HGVs 3.8% | 14,088 |
| A501 to New Oxford St Camden · 0.7 mi · HGVs 3.2% | 8,058 |
Source:DfT,UK Motoring analysis 2000 to 2025 Updated
Route
Camden to Islington · 6.3 miles
A400 traffic and collisions by section
15 sections between junctions, in route order. Each is the average of its DfT count points, weighted by length. 4 short link roads and spurs (1.1 miles) count in the road’s totals but are not listed.
Sections Tap a column heading to sort
| # | |||
|---|---|---|---|
| 1 | A501 to New Oxford StCamden | 8,058 | 57 |
| 2 | A3211 to Trafalgar SqWestminster | 12,879 | 3 |
| 3 | Trafalgar Sq to A401Westminster | 7,966 | 70 |
| 4 | A401 to A40Westminster | 3,578 | 44 |
| 5 | A40 to A5204Camden | 7,086 | 30 |
| 6 | A5204 to A501Camden | 11,035 | 44 |
| 7 | A501 to Harrington SqCamden | 17,240 | 35 |
| 8 | Harrington Sq to Camden High StCamden | 10,233 | 13 |
| 9 | Hampstead Rd to Delancey StCamden | 18,759 | 0 |
| 10 | Delancey St to A502Camden | 14,127 | 7 |
| 11 | A502 to A502/A503Camden | 6,127 | 14 |
| 12 | A502 to Royal College StCamden | 9,340 | 17 |
| 13 | Royal College St to A5200Camden | 14,088 | 103 |
| 14 | A5200 to A400 St Johns GroveIslington | 11,113 | 25 |
| 15 | Junction Rd to A1Islington | 3,915 | fewer than 3 |
Vehicles a day is the average daily flow in 2025. “Since 2019” compares the same count points. Collisions are those with the A400 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.
A400 traffic by vehicle type
Cars and taxis make up 59.7% of the vehicle miles on the A400. HGVs account for 3.7%.
Vehicle mix, 2025
Source:DfT,UK Motoring analysis 2000 to 2025 Updated
HGV share of traffic
| Year | HGV share |
|---|---|
| 2000 | 3.0% |
| 2001 | 3.0% |
| 2002 | 2.9% |
| 2003 | 2.4% |
| 2004 | 2.7% |
| 2005 | 2.9% |
| 2006 | 2.8% |
| 2007 | 3.0% |
| 2008 | 3.2% |
| 2009 | 3.4% |
| 2010 | 3.5% |
| 2011 | 3.8% |
| 2012 | 4.3% |
| 2013 | 4.5% |
| 2014 | 4.0% |
| 2015 | 3.9% |
| 2016 | 3.9% |
| 2017 | 3.8% |
| 2018 | 3.6% |
| 2019 | 3.3% |
| 2020 | 3.6% |
| 2021 | 3.6% |
| 2022 | 3.7% |
| 2023 | 3.6% |
| 2024 | 3.6% |
| 2025 | 3.7% |
Source:DfT,UK Motoring analysis 2000 to 2025 Updated
A400 traffic trend
Traffic on the A400 came to 25.2 million vehicle miles in 2025. At the count points present in both years, it is down 15.1% on 2019, before the pandemic, and down 29.8% on 2015.
Vehicle miles a year
Like for like, traffic is down 49.6% on 2000.
| Year | Vehicle miles |
|---|---|
| 2000 | 51m |
| 2001 | 50m |
| 2002 | 49m |
| 2003 | 49m |
| 2004 | 47m |
| 2005 | 47m |
| 2006 | 50m |
| 2007 | 49m |
| 2008 | 46m |
| 2009 | 44m |
| 2010 | 41m |
| 2011 | 40m |
| 2012 | 39m |
| 2013 | 38m |
| 2014 | 38m |
| 2015 | 36m |
| 2016 | 36m |
| 2017 | 37m |
| 2018 | 34m |
| 2019 | 30m |
| 2020 | 23m |
| 2021 | 24m |
| 2022 | 25m |
| 2023 | 26m |
| 2024 | 26m |
| 2025 | 25m |
Source:DfT,UK Motoring analysis 2000 to 2025 Updated
Average daily flow
| Year | Vehicles a day |
|---|---|
| 2000 | 21,881 |
| 2001 | 21,549 |
| 2002 | 20,743 |
| 2003 | 20,857 |
| 2004 | 19,893 |
| 2005 | 20,295 |
| 2006 | 21,418 |
| 2007 | 20,933 |
| 2008 | 19,500 |
| 2009 | 18,959 |
| 2010 | 17,476 |
| 2011 | 16,999 |
| 2012 | 16,531 |
| 2013 | 16,259 |
| 2014 | 16,367 |
| 2015 | 15,506 |
| 2016 | 15,412 |
| 2017 | 15,826 |
| 2018 | 14,831 |
| 2019 | 12,885 |
| 2020 | 9,844 |
| 2021 | 10,503 |
| 2022 | 11,021 |
| 2023 | 11,244 |
| 2024 | 11,285 |
| 2025 | 10,958 |
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, 2 of the 19 count points were counted; DfT estimated the rest from earlier counts and local trends.
A400 collisions
Police recorded 511 collisions with the A400 as the first road from 2021 to 2025, 86 of them fatal or serious. That is 404.0 per 100 million vehicle miles, higher than the 31.5 for all A-roads in Great Britain. On average there were 16.2 a year for each mile of road.
Reported collisions by year
Up 4.8% from 2021 to 2025.
| Year | Slight | Fatal or serious |
|---|---|---|
| 2021 | 86 | 18 |
| 2022 | 81 | 20 |
| 2023 | 78 | 17 |
| 2024 | 89 | 13 |
| 2025 | 91 | 18 |
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.
| Section | Per 100m vehicle miles |
|---|---|
| A501 to New Oxford St Camden · 57 collisions | 474.5 |
| Royal College St to A5200 Camden · 103 collisions | 468.6 |
| A501 to Harrington Sq Camden · 35 collisions | 186.7 |
Source:DfT STATS19,UK Motoring analysis 2021 to 2025 Updated
A further 80 collisions were recorded at junctions where the A400 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 A400
In route order. Each is the highway authority DfT files the count points under.
- Camden
- Westminster
- Islington
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 | 2000 to 2025 | 19 count points in 2025 | 15 September 2026 |
| Reported collisions | Road safety open data (STATS19) Department for Transport Derived statistics UK Motoring | 2021 to 2025 | 511 reported collisions | 15 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.