A-road
A478 traffic and collisions
The A478 is an A-road of 32.1 miles, from Pembrokeshire to Ceredigion. This page covers its traffic at 10 DfT count points since 2000 and the collisions police recorded on it.
- Traffic in 2025 48m vehicle miles
- Average daily traffic 4,097 vehicles a day, both directions
- Busiest section 7,717 A4218 Serpentine Rd to A477(T)
- HGV share 5.8% of vehicle miles
- Traffic since 2019 −5.6% same count points
- Collisions, 2021 to 2025 73 31.9 per 100m vehicle miles
How busy is the A478?
On an average day in 2025, 4,097 vehicles passed each point on the A478, counting both directions. The busiest section is A4218 Serpentine Rd to A477(T) (Pembrokeshire), with 7,717 a day; the quietest listed is A4139 White Lion St to A4218 Serpentine Rd, with 2,861.
Busiest sections, 2025
A4218 Serpentine Rd to A477(T) carries 1.9 times the road’s average flow.
| Section | Vehicles a day |
|---|---|
| A4218 Serpentine Rd to A477(T) Pembrokeshire · 4.0 mi · HGVs 3.1% | 7,717 |
| A477 to A4115 Pembrokeshire · 2.9 mi · HGVs 3.0% | 5,715 |
| A4115 to A40(T) Pembrokeshire · 4.3 mi · HGVs 3.9% | 3,807 |
| B4332E to A487 Pembrokeshire, Ceredigion · 4.9 mi · HGVs 5.4% | 3,487 |
| A40(T) to LA Boundry Pembrokeshire, Carmarthenshire · 8.8 mi · HGVs 9.0% | 3,387 |
| LA Boundry to B4332E Pembrokeshire · 6.2 mi · HGVs 10.4% | 2,976 |
| A4139 White Lion St to A4218 Serpentine Rd Pembrokeshire · 0.7 mi · HGVs 2.3% | 2,861 |
Source:DfT,UK Motoring analysis 2000 to 2025 Updated
Route
Pembrokeshire to Ceredigion · 32.1 miles
A478 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 | A478 to HarbourPembrokeshire | 1,180 | fewer than 3 |
| 2 | A4139 White Lion St to A4218 Serpentine RdPembrokeshire | 2,861 | 3 |
| 3 | A4218 Serpentine Rd to A477(T)Pembrokeshire | 7,717 | 16 |
| 4 | A477 to A4115Pembrokeshire | 5,715 | 5 |
| 5 | A4115 to A40(T)Pembrokeshire | 3,807 | 6 |
| 6 | A40(T) to LA BoundryPembrokeshire, Carmarthenshire | 3,387 | 9 |
| 7 | LA Boundry to B4332EPembrokeshire | 2,976 | 19 |
| 8 | B4332E to A487Pembrokeshire, Ceredigion | 3,487 | 13 |
Vehicles a day is the average daily flow in 2025. “Since 2019” compares the same count points. Collisions are those with the A478 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.
A478 traffic by vehicle type
Cars and taxis make up 72.8% of the vehicle miles on the A478. HGVs account for 5.8%, rising to 10.4% on LA Boundry to B4332E.
Vehicle mix, 2025
Source:DfT,UK Motoring analysis 2000 to 2025 Updated
HGV share of traffic
| Year | HGV share |
|---|---|
| 2000 | 6.2% |
| 2001 | 6.0% |
| 2002 | 6.3% |
| 2003 | 5.9% |
| 2004 | 5.9% |
| 2005 | 5.4% |
| 2006 | 5.9% |
| 2007 | 6.1% |
| 2008 | 6.2% |
| 2009 | 6.1% |
| 2010 | 5.8% |
| 2011 | 5.9% |
| 2012 | 6.0% |
| 2013 | 6.1% |
| 2014 | 6.2% |
| 2015 | 6.0% |
| 2016 | 5.9% |
| 2017 | 5.7% |
| 2018 | 5.7% |
| 2019 | 5.7% |
| 2020 | 6.7% |
| 2021 | 6.6% |
| 2022 | 6.3% |
| 2023 | 6.0% |
| 2024 | 5.9% |
| 2025 | 5.8% |
Source:DfT,UK Motoring analysis 2000 to 2025 Updated
A478 traffic trend
Traffic on the A478 came to 48 million vehicle miles in 2025. At the count points present in both years, it is down 5.6% on 2019, before the pandemic, and down 1.9% on 2015.
Vehicle miles a year
Like for like, traffic is up 4.4% on 2000.
| Year | Vehicle miles |
|---|---|
| 2000 | 45m |
| 2001 | 45m |
| 2002 | 40m |
| 2003 | 43m |
| 2004 | 44m |
| 2005 | 43m |
| 2006 | 45m |
| 2007 | 46m |
| 2008 | 45m |
| 2009 | 46m |
| 2010 | 45m |
| 2011 | 46m |
| 2012 | 45m |
| 2013 | 46m |
| 2014 | 47m |
| 2015 | 48m |
| 2016 | 50m |
| 2017 | 50m |
| 2018 | 50m |
| 2019 | 50m |
| 2020 | 38m |
| 2021 | 42m |
| 2022 | 45m |
| 2023 | 46m |
| 2024 | 47m |
| 2025 | 48m |
Source:DfT,UK Motoring analysis 2000 to 2025 Updated
Average daily flow
| Year | Vehicles a day |
|---|---|
| 2000 | 3,924 |
| 2001 | 3,967 |
| 2002 | 3,486 |
| 2003 | 3,745 |
| 2004 | 3,817 |
| 2005 | 3,749 |
| 2006 | 3,970 |
| 2007 | 3,989 |
| 2008 | 3,930 |
| 2009 | 4,004 |
| 2010 | 3,953 |
| 2011 | 3,995 |
| 2012 | 3,939 |
| 2013 | 3,993 |
| 2014 | 4,083 |
| 2015 | 4,195 |
| 2016 | 4,329 |
| 2017 | 4,331 |
| 2018 | 4,364 |
| 2019 | 4,343 |
| 2020 | 3,300 |
| 2021 | 3,646 |
| 2022 | 3,926 |
| 2023 | 4,005 |
| 2024 | 4,052 |
| 2025 | 4,097 |
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 (70.7% of today’s road for 2019). In 2025, 1 of the 10 count points were counted; DfT estimated the rest from earlier counts and local trends.
A478 collisions
Police recorded 73 collisions with the A478 as the first road from 2021 to 2025, 30 of them fatal or serious, including 3 fatal. That is 31.9 per 100 million vehicle miles, close to the 31.5 for all A-roads in Great Britain. On average there were 0.5 a year for each mile of road.
Reported collisions by year
Up 63.6% from 2021 to 2025.
| Year | Slight | Fatal or serious |
|---|---|---|
| 2021 | 5 | 6 |
| 2022 | 5 | 3 |
| 2023 | 12 | 5 |
| 2024 | 11 | 8 |
| 2025 | 10 | 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 |
|---|---|
| LA Boundry to B4332E Pembrokeshire · 19 collisions | 58.6 |
| B4332E to A487 Pembrokeshire, Ceredigion · 13 collisions | 43.4 |
| A4218 Serpentine Rd to A477(T) Pembrokeshire · 16 collisions | 29.6 |
Source:DfT STATS19,UK Motoring analysis 2021 to 2025 Updated
A further 3 collisions were recorded at junctions where the A478 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 A478
In route order. Each is the highway authority DfT files the count points under.
- Pembrokeshire
- Carmarthenshire
- Ceredigion
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 | 10 count points in 2025 | 15 September 2026 |
| Reported collisions | Road safety open data (STATS19) Department for Transport Derived statistics UK Motoring | 2021 to 2025 | 73 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.