A-road
A4147 traffic and collisions
The A4147 is an A-road of 8.3 miles, in Hertfordshire. This page covers its traffic at 5 DfT count points since 2000 and the collisions police recorded on it.
- Traffic in 2025 49m vehicle miles
- Average daily traffic 16,260 vehicles a day, both directions
- Busiest section 26,777 A5183 to King Harry Lane roundabout
- HGV share 1.1% of vehicle miles
- Traffic since 2019 −1.6% same count points
- Collisions, 2021 to 2025 57 24.5 per 100m vehicle miles
How busy is the A4147?
On an average day in 2025, 16,260 vehicles passed each point on the A4147, counting both directions. The busiest section is A5183 to King Harry Lane roundabout (Hertfordshire), with 26,777 a day; the quietest listed is King Harry Lane roundabout to Greenacres, Hemel Hempstead, with 9,816.
Busiest sections, 2025
A5183 to King Harry Lane roundabout carries 1.6 times the road’s average flow.
| Section | Vehicles a day |
|---|---|
| A5183 to King Harry Lane roundabout Hertfordshire · 0.7 mi · HGVs 0.7% | 26,777 |
| Roundabout with A4146/A4147 to Roundabout A414/A4147 Hertfordshire · 3.3 mi · HGVs 1.1% | 20,533 |
| A414 to Greenacres Hertfordshire · 0.8 mi · HGVs 1.4% | 17,360 |
| A1081 to A5183 Hertfordshire · 0.6 mi · HGVs 0.8% | 10,173 |
| King Harry Lane roundabout to Greenacres, Hemel Hempstead Hertfordshire · 2.9 mi · HGVs 1.4% | 9,816 |
Source:DfT,UK Motoring analysis 2000 to 2025 Updated
Route
In Hertfordshire · 8.3 miles
A4147 traffic and collisions by section
5 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 | A1081 to A5183Hertfordshire | 10,173 | 5 |
| 2 | A5183 to King Harry Lane roundaboutHertfordshire | 26,777 | 4 |
| 3 | King Harry Lane roundabout to Greenacres, Hemel HempsteadHertfordshire | 9,816 | 9 |
| 4 | A414 to GreenacresHertfordshire | 17,360 | 12 |
| 5 | Roundabout with A4146/A4147 to Roundabout A414/A4147Hertfordshire | 20,533 | 27 |
Vehicles a day is the average daily flow in 2025. “Since 2019” compares the same count points. Collisions are those with the A4147 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.
A4147 traffic by vehicle type
Cars and taxis make up 85.2% of the vehicle miles on the A4147. HGVs account for 1.1%.
Vehicle mix, 2025
Source:DfT,UK Motoring analysis 2000 to 2025 Updated
HGV share of traffic
| Year | HGV share |
|---|---|
| 2000 | 2.9% |
| 2001 | 2.8% |
| 2002 | 2.9% |
| 2003 | 3.4% |
| 2004 | 3.3% |
| 2005 | 3.3% |
| 2006 | 3.0% |
| 2007 | 3.2% |
| 2008 | 3.0% |
| 2009 | 2.6% |
| 2010 | 2.8% |
| 2011 | 2.7% |
| 2012 | 2.6% |
| 2013 | 2.7% |
| 2014 | 2.7% |
| 2015 | 2.6% |
| 2016 | 2.2% |
| 2017 | 2.3% |
| 2018 | 2.8% |
| 2019 | 2.6% |
| 2020 | 2.7% |
| 2021 | 1.4% |
| 2022 | 1.3% |
| 2023 | 1.2% |
| 2024 | 1.1% |
| 2025 | 1.1% |
Source:DfT,UK Motoring analysis 2000 to 2025 Updated
A4147 traffic trend
Traffic on the A4147 came to 49.3 million vehicle miles in 2025. At the count points present in both years, it is down 1.6% on 2019, before the pandemic, and down 9.9% on 2015.
Vehicle miles a year
Like for like, traffic is down 9.8% on 2000.
| Year | Vehicle miles |
|---|---|
| 2000 | 49m |
| 2001 | 53m |
| 2002 | 52m |
| 2003 | 49m |
| 2004 | 48m |
| 2005 | 48m |
| 2006 | 49m |
| 2007 | 49m |
| 2008 | 48m |
| 2009 | 47m |
| 2010 | 46m |
| 2011 | 50m |
| 2012 | 48m |
| 2013 | 48m |
| 2014 | 49m |
| 2015 | 50m |
| 2016 | 47m |
| 2017 | 48m |
| 2018 | 49m |
| 2019 | 49m |
| 2020 | 37m |
| 2021 | 41m |
| 2022 | 46m |
| 2023 | 48m |
| 2024 | 49m |
| 2025 | 49m |
Source:DfT,UK Motoring analysis 2000 to 2025 Updated
Average daily flow
| Year | Vehicles a day |
|---|---|
| 2000 | 17,117 |
| 2001 | 18,340 |
| 2002 | 17,975 |
| 2003 | 17,012 |
| 2004 | 16,545 |
| 2005 | 16,702 |
| 2006 | 17,118 |
| 2007 | 16,816 |
| 2008 | 16,648 |
| 2009 | 16,220 |
| 2010 | 16,061 |
| 2011 | 17,187 |
| 2012 | 16,643 |
| 2013 | 16,539 |
| 2014 | 17,001 |
| 2015 | 17,378 |
| 2016 | 16,310 |
| 2017 | 16,672 |
| 2018 | 17,073 |
| 2019 | 16,771 |
| 2020 | 12,614 |
| 2021 | 13,613 |
| 2022 | 15,181 |
| 2023 | 15,676 |
| 2024 | 16,155 |
| 2025 | 16,260 |
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 (60.2% of today’s road for 2019). In 2025, 0 of the 5 count points were counted; DfT estimated the rest from earlier counts and local trends.
A4147 collisions
Police recorded 57 collisions with the A4147 as the first road from 2021 to 2025, 13 of them fatal or serious. That is 24.5 per 100 million vehicle miles, lower than the 31.5 for all A-roads in Great Britain. On average there were 1.4 a year for each mile of road.
Reported collisions by year
Down 46.7% from 2021 to 2025.
| Year | Collisions |
|---|---|
| 2021 | 15 |
| 2022 | 12 |
| 2023 | 9 |
| 2024 | 13 |
| 2025 | 8 |
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 |
|---|---|
| A414 to Greenacres Hertfordshire · 12 collisions | 52.1 |
| Roundabout with A4146/A4147 to Roundabout A414/A4147 Hertfordshire · 27 collisions | 22.9 |
Source:DfT STATS19,UK Motoring analysis 2021 to 2025 Updated
A further 16 collisions were recorded at junctions where the A4147 was the second road; they are not in the figures above. Fatal or serious uses DfT’s adjusted serious figures. 100.0% of the collisions could be placed on a section. How we count collisions
Council areas on the A4147
In route order. Each is the highway authority DfT files the count points under.
- Hertfordshire
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 | 5 count points in 2025 | 15 September 2026 |
| Reported collisions | Road safety open data (STATS19) Department for Transport Derived statistics UK Motoring | 2021 to 2025 | 57 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.