The A road with the longest traffic delays in Wales

Martin Shipton

A road running through the centre of Cardiff records the greatest A-road vehicle delays in Wales, according to a new analysis of Department for Transport data.

Drivers using the A4161 face almost two minutes of extra journey time for every mile travelled.

Marshall Motor Group looked at 266 high-traffic local A-roads across Britain and compared journey times with free-flow conditions. The A4161 records the greatest delay among the 11 qualifying roads in Wales.

From east to west, the A4161 runs from Southern Way in Cardiff along Newport Road and through Dumfries Place, Stuttgarter Strasse and Boulevard de Nantes.

The route then follows the A470 along North Road, alongside Cardiff Castle and through to Duke Street, before becoming the A4161 again at Castle Street. It crosses Cardiff Bridge and continues along Cowbridge Road East, Wellington Street, Atlas Road, Lansdowne Road and Cowbridge Road East again, ending at the Ely Bridge roundabout on the A48.

The A4161 had the highest average delay of any locally managed A-road in Wales in 2025, at 118.8 seconds per vehicle per mile compared with free-flow conditions.

It was also the second-slowest, with vehicles averaging just 12.5mph. Only Cardiff’s A469 was slower, at 12.2mph.

The contrast with Wales as a whole is considerable. Across the Welsh roads in the road-level dataset, the median speed was 29.7mph and the median delay was 26.8 seconds per vehicle per mile.

Traffic on the A4161 was therefore travelling at well under half the median speed, while its delay was more than four times the median.

Cardiff also dominates the roads with the longest delays. Four of the six highest-delay road and local authority combinations are in the city.

The eight entries with the highest average delays were:

• A4161, Cardiff: 12.5mph; 118.8 seconds per vehicle per mile.
• A469, Cardiff: 12.2mph; 118.2 seconds per vehicle per mile.
• A4160, Cardiff: 13.3mph; 113.1 seconds per vehicle per mile.
• A4214, Carmarthenshire: 14.1mph; 99.1 seconds per vehicle per mile.
• A4216, Swansea: 14.1mph; 87.8 seconds per vehicle per mile.
• A4054, Cardiff: 14.8mph; 86.0 seconds per vehicle per mile.
• A4160, Vale of Glamorgan: 15.4mph; 85.4 seconds per vehicle per mile.
• A4119, Cardiff: 15.4mph; 79.8 seconds per vehicle per mile.

Marshall’s research included locally managed A-roads carrying at least 25,000 vehicles on an average day. Motorways were excluded.

Across Britain, the A217 through Hammersmith and Fulham had the greatest delay, at four minutes and 23 seconds per mile, while Wolverhampton’s A4150 had the greatest delay outside London, at two minutes and 12 seconds.

Ben Welham, motoring expert at Marshall Motor Group, said: “For commuters, a road that regularly adds a minute or two for every mile can make a real difference over the course of a week, especially when roadworks or incidents add to the usual congestion.

“The figures also show that high traffic levels don’t always mean long delays, with some very busy roads still keeping traffic moving well.”

Details of delays on more roads across Britain can be found here. 

---

Get more trusted Welsh news

Choose Nation.Cymru as a preferred source in Google News to see more of our journalism.