A-road
A355 traffic and collisions
The A355 is an A-road of 13.3 miles, from Windsor and Maidenhead to Buckinghamshire. This page covers its traffic at 13 DfT count points since 2000 and the collisions police recorded on it.
- Traffic in 2025 107m vehicle miles
- Average daily traffic 21,960 vehicles a day, both directions
- Busiest section 41,234 A332 to M4
- HGV share 3.9% of vehicle miles
- Traffic since 2019 +4.1% same count points
- Collisions, 2021 to 2025 162 33.3 per 100m vehicle miles
How busy is the A355?
On an average day in 2025, 21,960 vehicles passed each point on the A355, counting both directions. The busiest section is A332 to M4 (Windsor and Maidenhead, Slough), with 41,234 a day; the quietest listed is One Pin Lane to B416, with 14,032.
Busiest sections, 2025
A332 to M4 carries 1.9 times the road’s average flow.
| Section | Vehicles a day |
|---|---|
| A332 to M4 Windsor and Maidenhead, Slough · 0.5 mi · HGVs 1.4% | 41,234 |
| M4 to Church St Slough · 0.5 mi · HGVs 4.6% | 40,993 |
| M40 to A40 London Road roundabout Buckinghamshire · 0.6 mi · HGVs 3.4% | 37,241 |
| Roundabout A40/A355 to Amersham Buckinghamshire · 4.8 mi · HGVs 4.8% | 23,839 |
| One Pin Lane to M40 Buckinghamshire · 2.4 mi · HGVs 3.9% | 19,317 |
| A4 to One Pin Lane Slough, Buckinghamshire · 1.8 mi · HGVs 2.2% | 14,083 |
| One Pin Lane to B416 Buckinghamshire · 1.9 mi · HGVs 4.3% | 14,032 |
Source:DfT,UK Motoring analysis 2000 to 2025 Updated
Route
Windsor and Maidenhead to Buckinghamshire · 13.3 miles
A355 traffic and collisions by section
11 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 | A332 to M4Windsor and Maidenhead, Slough | 41,234 | fewer than 3 |
| 2 | M4 to Church StSlough | 40,993 | 15 |
| 3 | ChurchSt to A4Slough | 32,794 | 14 |
| 4 | A4 to One Pin LaneSlough, Buckinghamshire | 14,083 | 80 |
| 5 | One Pin Lane to B416Buckinghamshire | 14,032 | 14 |
| 6 | One Pin Lane to M40Buckinghamshire | 19,317 | 18 |
| 7 | M40 to A40 London Road roundaboutBuckinghamshire | 37,241 | fewer than 3 |
| 8 | Roundabout A40/A355 to AmershamBuckinghamshire | 23,839 | 14 |
| 9 | A413 to BroadwayBuckinghamshire | 19,973 | fewer than 3 |
| 10 | Broadway to A416Buckinghamshire | 19,973 | 0 |
| 11 | A416 to A404Buckinghamshire | 10,852 | 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 A355 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.
A355 traffic by vehicle type
Cars and taxis make up 80.8% of the vehicle miles on the A355. HGVs account for 3.9%.
Vehicle mix, 2025
Source:DfT,UK Motoring analysis 2000 to 2025 Updated
HGV share of traffic
| Year | HGV share |
|---|---|
| 2000 | 4.2% |
| 2001 | 4.2% |
| 2002 | 4.1% |
| 2003 | 4.2% |
| 2004 | 4.3% |
| 2005 | 4.2% |
| 2006 | 3.6% |
| 2007 | 3.5% |
| 2008 | 3.4% |
| 2009 | 3.2% |
| 2010 | 3.0% |
| 2011 | 2.7% |
| 2012 | 2.8% |
| 2013 | 3.0% |
| 2014 | 2.9% |
| 2015 | 3.0% |
| 2016 | 2.9% |
| 2017 | 2.8% |
| 2018 | 2.8% |
| 2019 | 3.0% |
| 2020 | 3.6% |
| 2021 | 3.8% |
| 2022 | 4.5% |
| 2023 | 4.2% |
| 2024 | 4.0% |
| 2025 | 3.9% |
Source:DfT,UK Motoring analysis 2000 to 2025 Updated
A355 traffic trend
Traffic on the A355 came to 107 million vehicle miles in 2025. At the count points present in both years, it is up 4.1% on 2019, before the pandemic, and down 1.1% on 2015.
Vehicle miles a year
Like for like, traffic is up 14.8% on 2000.
| Year | Vehicle miles |
|---|---|
| 2000 | 92m |
| 2001 | 88m |
| 2002 | 86m |
| 2003 | 88m |
| 2004 | 91m |
| 2005 | 88m |
| 2006 | 94m |
| 2007 | 94m |
| 2008 | 90m |
| 2009 | 89m |
| 2010 | 91m |
| 2011 | 93m |
| 2012 | 89m |
| 2013 | 88m |
| 2014 | 90m |
| 2015 | 95m |
| 2016 | 94m |
| 2017 | 94m |
| 2018 | 98m |
| 2019 | 97m |
| 2020 | 72m |
| 2021 | 79m |
| 2022 | 92m |
| 2023 | 103m |
| 2024 | 106m |
| 2025 | 107m |
Source:DfT,UK Motoring analysis 2000 to 2025 Updated
Average daily flow
| Year | Vehicles a day |
|---|---|
| 2000 | 20,036 |
| 2001 | 19,098 |
| 2002 | 18,755 |
| 2003 | 19,184 |
| 2004 | 19,677 |
| 2005 | 19,063 |
| 2006 | 20,431 |
| 2007 | 20,380 |
| 2008 | 19,619 |
| 2009 | 19,375 |
| 2010 | 19,842 |
| 2011 | 20,287 |
| 2012 | 19,393 |
| 2013 | 19,150 |
| 2014 | 19,655 |
| 2015 | 20,552 |
| 2016 | 20,471 |
| 2017 | 20,345 |
| 2018 | 20,775 |
| 2019 | 20,487 |
| 2020 | 15,385 |
| 2021 | 16,605 |
| 2022 | 19,017 |
| 2023 | 21,259 |
| 2024 | 21,728 |
| 2025 | 21,960 |
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 (49.6% of today’s road for 2019). In 2025, 2 of the 13 count points were counted; DfT estimated the rest from earlier counts and local trends.
A355 collisions
Police recorded 162 collisions with the A355 as the first road from 2021 to 2025, fewer than 3 of them fatal or serious. That is 33.3 per 100 million vehicle miles, close to the 31.5 for all A-roads in Great Britain. On average there were 2.4 a year for each mile of road.
Reported collisions by year
Down 9.4% from 2021 to 2025.
| Year | Collisions |
|---|---|
| 2021 | 32 |
| 2022 | 34 |
| 2023 | 35 |
| 2024 | 32 |
| 2025 | 29 |
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 |
|---|---|
| A4 to One Pin Lane Slough, Buckinghamshire · 80 collisions | 181.1 |
| M4 to Church St Slough · 15 collisions | 40.7 |
| One Pin Lane to B416 Buckinghamshire · 14 collisions | 30.0 |
| One Pin Lane to M40 Buckinghamshire · 18 collisions | 24.5 |
| Roundabout A40/A355 to Amersham Buckinghamshire · 14 collisions | 8.7 |
Source:DfT STATS19,UK Motoring analysis 2021 to 2025 Updated
A further 36 collisions were recorded at junctions where the A355 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 A355
In route order. Each is the highway authority DfT files the count points under.
- Windsor and Maidenhead
- Slough
- Buckinghamshire
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 | 13 count points in 2025 | 15 September 2026 |
| Reported collisions | Road safety open data (STATS19) Department for Transport Derived statistics UK Motoring | 2021 to 2025 | 162 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.