M25’s worst traffic hotspots revealed as motorway turns 40

The M25 turns 40 on 29 October, with new research revealing that journeys on one particular stretch take more than three times as long at the afternoon peak as later in the evening.

Vehicle data company Geotab found that all eight of the most congested stretches were between junctions 10 and 20, around the M3, M4 and M40 interchanges, particularly near London’s Heathrow airport.

The clockwise journey from junction 14 to junction 15, towards the M4, averaged 9.2 minutes at 4pm, compared with three minutes at 7pm. Further north, travelling anticlockwise from Mill End towards Denham, between junctions 17 and 16, took 15.6 minutes at 7am and 6.6 minutes at 7pm.

The analysis covered 12 sample weeks between September 2025 and August 2026, across 46 of the 58 sections, counting each direction separately. In total, vehicles averaged at least 80 per cent of the posted speed limit.

There are some less obvious landmarks along the 117-mile route, too. Near Epping, the Bell Common Tunnel runs beneath a cricket ground, reinstated after construction. Some two million trees were planted as the motorway was built, helping it settle into the surrounding countryside.

For businesses, however, appreciating the scenery is unlikely to compensate for missed appointments. The survey of 1,000 van drivers from the South East who regularly use the M25 found a quarter had declined jobs because journeys could be too unpredictable. Three in ten reported customer complaints, while 29 per cent cited higher fuel costs.

However, 84 per cent said their businesses couldn’t operate as effectively without the motorway, and four in five considered the alternatives worse. The road whose queues helped inspire Chris Rea’s 1989 hit The Road to Hell remains difficult to avoid.

Some of the M25’s roadside features have attracted considerably more affection. The “Give Peas a Chance” graffiti on the Chalfont Viaduct, between junctions 16 and 17, had a Facebook following of more than 8,000. When it was painted over in 2018, a petition called for its restoration and protection.

Spending hours on London’s orbital motorway hasn’t always been unwelcomed, though. In 2012, a four-hour sightseeing coach trip around it sold out at £15 a head, prompting extra dates. Heathrow’s Terminal 5 was among the attractions, although most drivers manage to spend an afternoon on the M25 without a tour guide.

Even the motorway’s familiar shape comes with a qualification: the Dartford Crossing is officially the A282, so the M25 doesn’t quite complete a circle. Margaret Thatcher opened its final section in 1986, and its first service area, South Mimms, which followed in 1987.

Today’s regulars have a different wish list. Faster incident detection and clearance was the most popular improvement in the survey, selected by 11.7 per cent, narrowly ahead of a consistent 50mph limit at peak times and better coordination of roadworks. Better traffic information also ranked ahead of extra lanes on the worst stretches.

There’s plenty of disruption to tackle. Across the sample, Geotab recorded 659 periods when a section’s speed fell to 70 per cent or less of its normal level, including 236 lasting at least two hours. Monday and Friday had the most disruptions.

Geotab vice-president Aaron Jarvis said, “Some congestion is inevitable on a motorway this busy, so the aim is to manage it better. The data shows where and when the pressure points are, so fleets can adjust departure times and plan around the weekday peaks.”