South Wales traffic: M4 and A470 rush-hour delays in October 2026

Key Points

• Motorists throughout South Wales experienced traffic problems during rush hour on Monday morning, October 5, 2026, on both the M4 and A470 motorways.
• Roadworks and maintenance work that was carried out overnight continued for the rest of the week causing delays.
• The following is the list of active alerts provided by Traffic Wales – closure of exit slip from M4 junction 35 (Pencoed), surveying works on the A470 between Abercynon and Nantgarw.
• There are ongoing works on the A470 at Llanrwst and also A40 at Tarell Roundabout.

Wales (Wales Times) October 05, 2026 — Drivers across South Wales are dealing with rush-hour congestion this morning, while overnight roadworks continue on key routes into the week. Traffic built on the M4 and A470 as commuters began their journeys, with planned closures and maintenance activities contributing to slower-moving traffic on two of the region’s busiest corridors.

What is causing M4 and A470 delays during Monday’s rush hour?

As reported by traffic-monitoring services and regional outlets, the delays stem from a combination of peak demand and scheduled engineering work. Traffic Wales’ live alerts show overnight and early-morning restrictions on the M4 at junction 35 (Pencoed), where the exit slip road is closed for clearance work between 19:00 and 06:00 until October 9. On the A470, survey-related works between Abercynon and Nantgarw have involved lane closures and entry-slip restrictions overnight, running through to October 8.

Where exactly are the roadworks affecting South Wales commuters?

The most prominent M4 disruption this week is at junction 35 Pencoed, where the exit slip closure and diversions are in effect nightly. Further west, a bridge resurfacing project between junctions 37 (Pyle) and 38 (Margam) was scheduled over the weekend into early October, with overnight closures between 20:00 and 06:00.

On the A470, two separate stretches are relevant to southbound and northbound flows around uk/local/cardiff/">Cardiff and the Valleys. Between Abercynon and Nantgarw, entry slip roads have been closed in both directions with one lane shut for surveys, according to Traffic Wales. Further north, a longer-term resurfacing scheme at Llanrwst operates under a 10mph convoy with temporary traffic lights and a 3.25m width restriction, running daily from 07:00 to 02:00 until October 24.

How long will the current M4 and A470 disruptions last?

Current alerts indicate that M4 junction 35 works are due to conclude on October 9, assuming no extensions. The A470 Abercynon–Nantgarw survey works are listed until October 8. The Llanrwst resurfacing on the A470 is a multi-week operation, scheduled until October 24. Associated A40 works at Tarell Roundabout, linked to A470 resurfacing, are also active, with one lane closed until October 23 and full closures with diversions in some periods until October 12.

What have traffic authorities advised drivers to do?

Traffic Wales and regional reporting have consistently advised motorists to plan ahead, allow additional travel time and check live updates before setting off. Where feasible, drivers are encouraged to consider alternative routes to avoid the worst-affected sections during peak hours. Official guidance also highlights the importance of observing temporary signage and diversion routes around closure points, particularly at night when capacities are reduced.

Which other roads in Wales are affected by planned closures this week?

Beyond the M4 and A470, several other routes show scheduled disruptions. The A483 around Rossett and Gresford has overnight maintenance with slip-road closures and diversions in early October. The A4076 between Steynton and the A477 interchange is closed for maintenance on selected nights until mid-November. These works, while not always coinciding with morning peaks, can compound regional congestion when they overlap with commuter flows or incident-related delays.

How are M4 junction 35 and A470 Nantgarw works coordinated?

According to Traffic Wales’ published alerts, the M4 junction 35 exit-slip closure is part of a clearance programme running nightly from September 15 to October 9. The A470 Abercynon–Nantgarw survey works, with entry-slip closures and a single-lane restriction, are timed overnight from September 24 to October 8. Both schemes are designed to limit daytime impact, but residual effects can persist into early morning periods as traffic clears and normal lane configurations are restored.

What background explains these M4 and A470 developments?

The current pattern of overnight closures reflects a wider programme of maintenance and resurfacing across Wales’ strategic road network. The M4, as the primary east–west motorway serving Newport, Cardiff and Swansea, requires periodic clearance, bridge works and resurfacing to maintain capacity and safety. Similarly, the A470, which links Cardiff with the Valleys and mid-Wales, is subject to scheduled surveys and resurfacing to address wear from high traffic volumes and weather-related stress. The overlap of several schemes in late September and early October has concentrated disruption on key commuter corridors, increasing the likelihood of rush-hour delays when works run late or when incidents occur nearby.

What predictions can be made for commuters and local businesses?

If the scheduled end dates hold, M4 junction 35 and A470 Abercynon–Nantgarw works should ease by the second week of October, potentially reducing morning congestion on those specific stretches. However, the longer A470 Llanrwst resurfacing and associated A40 works will continue to affect north south flows beyond that point, particularly for longer-distance traffic and freight. For daily commuters, the most likely impact is continued variability in journey times during peak hours, with occasional knock-on effects when incidents coincide with reduced capacity. Local businesses that depend on reliable road access such as logistics firms, tradespeople and shift workers may need to build additional buffer time into schedules until the cluster of closures subsides.