A-road
A4146 traffic and collisions
The A4146 is an A-road of 16.6 miles, from Hertfordshire to Milton Keynes. This page covers its traffic at 12 DfT count points since 2000 and the collisions police recorded on it.
- Traffic in 2025 152m vehicle miles
- Average daily traffic 25,013 vehicles a day, both directions
- Busiest section 34,975 A421 to Childs Way
- HGV share 5.2% of vehicle miles
- Traffic since 2019 +7.6% same count points
- Collisions, 2021 to 2025 108 15.0 per 100m vehicle miles
How busy is the A4146?
On an average day in 2025, 25,013 vehicles passed each point on the A4146, counting both directions. The busiest section is A421 to Childs Way (Milton Keynes), with 34,975 a day; the quietest listed is A4251 to A414, with 15,450.
Busiest sections, 2025
A421 to Childs Way carries 1.4 times the road’s average flow.
| Section | Vehicles a day |
|---|---|
| A421 to Childs Way Milton Keynes · 1.4 mi · HGVs 5.9% | 34,975 |
| Tongwell St to A509 Milton Keynes · 0.5 mi · HGVs 5.9% | 31,827 |
| Bletcham Rndbt (A5) to Brinklow Rndbt (A421 Milton Keynes · 2.8 mi · HGVs 4.6% | 27,390 |
| A4146 to A418 Central Bedfordshire, Buckinghamshire · 1.2 mi · HGVs 4.0% | 26,121 |
| A418 to A5 Central Bedfordshire, Buckinghamshire, Milton Keynes · 7.7 mi · HGVs 6.2% | 24,275 |
| Roundabout A4146/A4147 to Roundabout with A414/A4146 Hertfordshire · 1.6 mi · HGVs 0.9% | 19,811 |
| A4012 to A505 Central Bedfordshire · 0.8 mi · HGVs 5.8% | 18,017 |
| A4251 to A414 Hertfordshire · 0.6 mi · HGVs 1.7% | 15,450 |
Source:DfT,UK Motoring analysis 2000 to 2025 Updated
Route
Hertfordshire to Milton Keynes · 16.6 miles
A4146 traffic and collisions by section
8 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 | A4251 to A414Hertfordshire | 15,450 | 8 |
| 2 | Roundabout A4146/A4147 to Roundabout with A414/A4146Hertfordshire | 19,811 | 19 |
| 3 | A4012 to A505Central Bedfordshire | 18,017 | 10 |
| 4 | A4146 to A418Central Bedfordshire, Buckinghamshire | 26,121 | 3 |
| 5 | A418 to A5Central Bedfordshire, Buckinghamshire, Milton Keynes | 24,275 | 26 |
| 6 | Bletcham Rndbt (A5) to Brinklow Rndbt (A421Milton Keynes | 27,390 | 12 |
| 7 | A421 to Childs WayMilton Keynes | 34,975 | 15 |
| 8 | Tongwell St to A509Milton Keynes | 31,827 | 8 |
Vehicles a day is the average daily flow in 2025. “Since 2019” compares the same count points. Collisions are those with the A4146 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.
A4146 traffic by vehicle type
Cars and taxis make up 79.9% of the vehicle miles on the A4146. HGVs account for 5.2%.
Vehicle mix, 2025
Source:DfT,UK Motoring analysis 2000 to 2025 Updated
HGV share of traffic
| Year | HGV share |
|---|---|
| 2000 | 4.0% |
| 2001 | 4.6% |
| 2002 | 4.8% |
| 2003 | 4.8% |
| 2004 | 4.9% |
| 2005 | 4.3% |
| 2006 | 4.5% |
| 2007 | 5.5% |
| 2008 | 5.4% |
| 2009 | 4.9% |
| 2010 | 5.1% |
| 2011 | 5.1% |
| 2012 | 5.4% |
| 2013 | 5.6% |
| 2014 | 5.5% |
| 2015 | 5.6% |
| 2016 | 5.1% |
| 2017 | 5.2% |
| 2018 | 5.0% |
| 2019 | 5.2% |
| 2020 | 6.4% |
| 2021 | 6.9% |
| 2022 | 6.1% |
| 2023 | 5.5% |
| 2024 | 5.2% |
| 2025 | 5.2% |
Source:DfT,UK Motoring analysis 2000 to 2025 Updated
A4146 traffic trend
Traffic on the A4146 came to 152 million vehicle miles in 2025. At the count points present in both years, it is up 7.6% on 2019, before the pandemic, and up 19.7% on 2015.
Vehicle miles a year
Like for like, traffic is up 42.7% on 2000.
| Year | Vehicle miles |
|---|---|
| 2000 | 128m |
| 2001 | 126m |
| 2002 | 124m |
| 2003 | 123m |
| 2004 | 132m |
| 2005 | 125m |
| 2006 | 130m |
| 2007 | 134m |
| 2008 | 148m |
| 2009 | 141m |
| 2010 | 138m |
| 2011 | 139m |
| 2012 | 137m |
| 2013 | 155m |
| 2014 | 159m |
| 2015 | 165m |
| 2016 | 168m |
| 2017 | 170m |
| 2018 | 142m |
| 2019 | 150m |
| 2020 | 113m |
| 2021 | 132m |
| 2022 | 139m |
| 2023 | 146m |
| 2024 | 153m |
| 2025 | 152m |
Source:DfT,UK Motoring analysis 2000 to 2025 Updated
Average daily flow
| Year | Vehicles a day |
|---|---|
| 2000 | 13,020 |
| 2001 | 12,801 |
| 2002 | 12,625 |
| 2003 | 12,543 |
| 2004 | 13,430 |
| 2005 | 12,745 |
| 2006 | 12,810 |
| 2007 | 13,233 |
| 2008 | 14,307 |
| 2009 | 14,126 |
| 2010 | 13,829 |
| 2011 | 13,905 |
| 2012 | 13,724 |
| 2013 | 15,541 |
| 2014 | 15,917 |
| 2015 | 16,596 |
| 2016 | 16,834 |
| 2017 | 17,068 |
| 2018 | 24,928 |
| 2019 | 24,719 |
| 2020 | 18,621 |
| 2021 | 21,812 |
| 2022 | 22,915 |
| 2023 | 24,137 |
| 2024 | 25,203 |
| 2025 | 25,013 |
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 (47.6% of today’s road for 2019). In 2025, 1 of the 12 count points were counted; DfT estimated the rest from earlier counts and local trends.
A4146 collisions
Police recorded 108 collisions with the A4146 as the first road from 2021 to 2025, 26 of them fatal or serious, including 3 fatal. That is 15.0 per 100 million vehicle miles, lower than the 31.5 for all A-roads in Great Britain. On average there were 1.3 a year for each mile of road.
Reported collisions by year
Up 91.7% from 2021 to 2025.
| Year | Slight | Fatal or serious |
|---|---|---|
| 2021 | 9 | 3 |
| 2022 | 17 | 9 |
| 2023 | 18 | 5 |
| 2024 | 19 | 5 |
| 2025 | 19 | 4 |
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 |
|---|---|
| A4012 to A505 Central Bedfordshire · 10 collisions | 39.5 |
| Roundabout A4146/A4147 to Roundabout with A414/A4146 Hertfordshire · 19 collisions | 33.9 |
| A421 to Childs Way Milton Keynes · 15 collisions | 17.1 |
| Bletcham Rndbt (A5) to Brinklow Rndbt (A421 Milton Keynes · 12 collisions | 9.9 |
| A418 to A5 Central Bedfordshire, Buckinghamshire, Milton Keynes · 26 collisions | 7.8 |
Source:DfT STATS19,UK Motoring analysis 2021 to 2025 Updated
A further 36 collisions were recorded at junctions where the A4146 was the second road; they are not in the figures above. Fatal or serious uses DfT’s adjusted serious figures. 93.5% of the collisions could be placed on a section. How we count collisions
Council areas on the A4146
In route order. Each is the highway authority DfT files the count points under.
- Hertfordshire
- Central Bedfordshire
- Buckinghamshire
- Milton Keynes
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 | 12 count points in 2025 | 15 September 2026 |
| Reported collisions | Road safety open data (STATS19) Department for Transport Derived statistics UK Motoring | 2021 to 2025 | 108 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.