Trunk A-road
A420 traffic and collisions
The A420 is a trunk A-road of 53.3 miles, from Oxfordshire to City of Bristol. This page covers its traffic at 38 DfT count points since 2000 and the collisions police recorded on it.
- Traffic in 2025 297m vehicle miles
- Average daily traffic 15,243 vehicles a day, both directions
- Busiest section 25,499 At A417
- HGV share 5.5% of vehicle miles
- Traffic since 2019 −3.7% same count points
- Collisions, 2021 to 2025 683 48.8 per 100m vehicle miles
How busy is the A420?
On an average day in 2025, 15,243 vehicles passed each point on the A420, counting both directions. The busiest section is At A417 (Oxfordshire), with 25,499 a day; the quietest listed is Longwall St to Speedwell St, with 3,488.
Busiest sections, 2025
At A417 carries 1.7 times the road’s average flow.
| Section | Vehicles a day |
|---|---|
| At A417 Oxfordshire · 0.5 mi · HGVs 7.1% | 25,499 |
| A338 Tobney Wood to A34 Botley Oxfordshire · 4.8 mi · HGVs 7.9% | 21,545 |
| A 417 Junction SOUTH Faringdon to supermarket roundabout Oxfordshire, Swindon · 9.0 mi · HGVs 7.7% | 19,588 |
| A415 Rnbt Kingston Bagpuize to A417 Junction FARINGDON Oxfordshire · 7.6 mi · HGVs 6.7% | 19,167 |
| B4467 to A4320 City of Bristol · 0.9 mi · HGVs 1.3% | 18,469 |
| A415 Junction Kingston Bagpuize to A 338 Junction Oxfordshire · 3.2 mi · HGVs 8.3% | 17,274 |
| A431 to B4467 City of Bristol · 0.5 mi · HGVs 0.9% | 17,249 |
| A34(T) to Hollybush Row Oxfordshire · 1.5 mi · HGVs 1.7% | 16,496 |
| Botley Road to Thames St/Speedwell St Oxfordshire · 0.5 mi · HGVs 1.6% | 14,128 |
| The Plain to A420 London Rd Oxfordshire · 2.2 mi · HGVs 0.9% | 13,494 |
Source:DfT,UK Motoring analysis 2000 to 2025 Updated
Route
Oxfordshire to City of Bristol · 53.3 miles in 2 stretches
A420 traffic and collisions by section
30 sections between junctions, in route order (2 separate stretches). Each is the average of its DfT count points, weighted by length. 5 short link roads and spurs (0.8 miles) count in the road’s totals but are not listed.
Show all 30 sections Tap a column heading to sort
| # | |||
|---|---|---|---|
| 1 | The Plain to A420 London RdOxfordshire · stretch 1 | 13,494 | 129 |
| 2 | A4158 Iffley Road roundabout to Longwall StOxfordshire · stretch 1 | 14,115 | 21 |
| 3 | Longwall St to Speedwell StOxfordshire · stretch 1 | 3,488 | 38 |
| 4 | Thames St to St AldgatesOxfordshire · stretch 1 | 3,837 | fewer than 3 |
| 5 | Botley Road to Thames St/Speedwell StOxfordshire · stretch 1 | 14,128 | 15 |
| 6 | A34(T) to Hollybush RowOxfordshire · stretch 1 | 16,496 | 44 |
| 7 | A338 Tobney Wood to A34 BotleyOxfordshire · stretch 1 | 21,545 | 14 |
| 8 | A415 Junction Kingston Bagpuize to A 338 JunctionOxfordshire · stretch 1 | 17,274 | 7 |
| 9 | A415 Rnbt Kingston Bagpuize to A417 Junction FARINGDONOxfordshire · stretch 1 | 19,167 | 39 |
| 10 | At A417Oxfordshire · stretch 1 | 25,499 | fewer than 3 |
| 11 | A 417 Junction SOUTH Faringdon to supermarket roundaboutOxfordshire, Swindon · stretch 1 | 19,588 | 50 |
| 12 | supermarket roundabout to A419Swindon · stretch 1 | 23,081 | 17 |
| 13 | A4 to A420 SplitWiltshire · stretch 2 | 17,496 | fewer than 3 |
| 14 | Marshfield Rd/Audley Rd to Ivy LaneWiltshire · stretch 2 | 11,193 | 6 |
| 15 | B4528 Hardenhuish Lane to Park LaneWiltshire · stretch 2 | 12,979 | 8 |
| 16 | B4528 N to A350Wiltshire · stretch 2 | 16,383 | 3 |
| 17 | A350 to B4039Wiltshire · stretch 2 | 13,424 | 19 |
| 18 | B4039 to A46(T)Wiltshire, South Gloucestershire · stretch 2 | 7,467 | 36 |
| 19 | A4175 Bath Road to Bath RoadSouth Gloucestershire · stretch 2 | 12,659 | 32 |
| 20 | At A4175South Gloucestershire · stretch 2 | 10,059 | 4 |
| 21 | At A4175South Gloucestershire · stretch 2 | 17,271 | 4 |
| 22 | A4017 to A4174South Gloucestershire · stretch 2 | 11,786 | 6 |
| 23 | A4174 to A4017South Gloucestershire · stretch 2 | 7,184 | 5 |
| 24 | At A4017South Gloucestershire, City of Bristol · stretch 2 | 8,706 | 5 |
| 25 | A4017 to A431City of Bristol · stretch 2 | 9,373 | 36 |
| 26 | A431 to B4467City of Bristol · stretch 2 | 17,249 | 25 |
| 27 | B4467 to A4320City of Bristol · stretch 2 | 18,469 | 62 |
| 28 | Easton Way roundabout to Trinity RdCity of Bristol · stretch 2 | 17,331 | 13 |
| 29 | Trinity Rd to Midland RdCity of Bristol · stretch 2 | 12,508 | 8 |
| 30 | A4044 to A420 splitCity of Bristol · stretch 2 | 16,859 | 21 |
Vehicles a day is the average daily flow in 2025. “Since 2019” compares the same count points. Collisions are those with the A420 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.
A420 traffic by vehicle type
Cars and taxis make up 75.4% of the vehicle miles on the A420. HGVs account for 5.5%, rising to 8.3% on A415 Junction Kingston Bagpuize to A 338 Junction.
Vehicle mix, 2025
Source:DfT,UK Motoring analysis 2000 to 2025 Updated
HGV share of traffic
| Year | HGV share |
|---|---|
| 2000 | 8.1% |
| 2001 | 7.6% |
| 2002 | 7.2% |
| 2003 | 7.3% |
| 2004 | 7.3% |
| 2005 | 7.0% |
| 2006 | 7.2% |
| 2007 | 7.1% |
| 2008 | 6.8% |
| 2009 | 6.1% |
| 2010 | 6.2% |
| 2011 | 6.2% |
| 2012 | 6.5% |
| 2013 | 6.6% |
| 2014 | 6.1% |
| 2015 | 6.2% |
| 2016 | 6.0% |
| 2017 | 5.8% |
| 2018 | 5.8% |
| 2019 | 5.8% |
| 2020 | 6.9% |
| 2021 | 7.0% |
| 2022 | 6.8% |
| 2023 | 6.4% |
| 2024 | 5.9% |
| 2025 | 5.5% |
Source:DfT,UK Motoring analysis 2000 to 2025 Updated
A420 traffic trend
Traffic on the A420 came to 297 million vehicle miles in 2025. At the count points present in both years, it is down 3.7% on 2019, before the pandemic, and about the same as in 2015.
Vehicle miles a year
Like for like, traffic is up 2.1% on 2000.
| Year | Vehicle miles |
|---|---|
| 2000 | 290m |
| 2001 | 295m |
| 2002 | 289m |
| 2003 | 293m |
| 2004 | 303m |
| 2005 | 301m |
| 2006 | 294m |
| 2007 | 291m |
| 2008 | 293m |
| 2009 | 288m |
| 2010 | 287m |
| 2011 | 288m |
| 2012 | 277m |
| 2013 | 277m |
| 2014 | 286m |
| 2015 | 295m |
| 2016 | 302m |
| 2017 | 307m |
| 2018 | 307m |
| 2019 | 309m |
| 2020 | 236m |
| 2021 | 257m |
| 2022 | 277m |
| 2023 | 283m |
| 2024 | 288m |
| 2025 | 297m |
Source:DfT,UK Motoring analysis 2000 to 2025 Updated
Average daily flow
| Year | Vehicles a day |
|---|---|
| 2000 | 14,994 |
| 2001 | 15,239 |
| 2002 | 14,941 |
| 2003 | 15,141 |
| 2004 | 15,652 |
| 2005 | 15,582 |
| 2006 | 15,207 |
| 2007 | 15,027 |
| 2008 | 15,125 |
| 2009 | 14,880 |
| 2010 | 14,832 |
| 2011 | 14,879 |
| 2012 | 14,316 |
| 2013 | 14,315 |
| 2014 | 14,760 |
| 2015 | 15,238 |
| 2016 | 15,629 |
| 2017 | 15,882 |
| 2018 | 15,706 |
| 2019 | 15,807 |
| 2020 | 12,074 |
| 2021 | 13,148 |
| 2022 | 14,248 |
| 2023 | 14,552 |
| 2024 | 14,807 |
| 2025 | 15,243 |
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, 7 of the 38 count points were counted; DfT estimated the rest from earlier counts and local trends.
A420 collisions
Police recorded 683 collisions with the A420 as the first road from 2021 to 2025, 167 of them fatal or serious, including 7 fatal. That is 48.8 per 100 million vehicle miles, higher than the 31.5 for all A-roads in Great Britain. On average there were 2.6 a year for each mile of road.
Reported collisions by year
Down 9.2% from 2021 to 2025.
| Year | Slight | Fatal or serious |
|---|---|---|
| 2021 | 100 | 31 |
| 2022 | 109 | 35 |
| 2023 | 103 | 28 |
| 2024 | 120 | 38 |
| 2025 | 85 | 34 |
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 |
|---|---|
| Longwall St to Speedwell St Oxfordshire · 38 collisions | 1,019.0 |
| The Plain to A420 London Rd Oxfordshire · 129 collisions | 279.3 |
| B4467 to A4320 City of Bristol · 62 collisions | 211.2 |
| A4017 to A431 City of Bristol · 36 collisions | 167.2 |
| A431 to B4467 City of Bristol · 25 collisions | 164.5 |
| Botley Road to Thames St/Speedwell St Oxfordshire · 15 collisions | 120.2 |
| A34(T) to Hollybush Row Oxfordshire · 44 collisions | 100.6 |
| A350 to B4039 Wiltshire · 19 collisions | 67.3 |
Source:DfT STATS19,UK Motoring analysis 2021 to 2025 Updated
A further 72 collisions were recorded at junctions where the A420 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 A420
In route order. Each is the highway authority DfT files the count points under.
- Oxfordshire
- Swindon
- Wiltshire
- South Gloucestershire
- City of Bristol
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 | 38 count points in 2025 | 15 September 2026 |
| Reported collisions | Road safety open data (STATS19) Department for Transport Derived statistics UK Motoring | 2021 to 2025 | 683 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.