The M25, London's orbital motorway, is not technically a complete circle. The section crossing the River Thames at the Dartford Crossing is officially designated the A282, not the M25, according to a report by sister title London Now. This means drivers who believe they have completed a full lap of the M25 have, in fact, spent part of the journey on an A-road.
Why the M25 Becomes the A282 at Dartford
The designation change exists because the Dartford Crossing predates the M25. The first Dartford Tunnel opened in 1963, with a second tunnel added in 1980. The M25, by contrast, was built in stages and only completed as a circular route in 1986. When the motorway was constructed, it connected to the existing road at Dartford rather than absorbing it into the M25 designation.
Government documents from 1978, covering the Dartford-to-Swanley section of the M25, already referred to the road at Dartford as the South Orbital Road, A282. The Queen Elizabeth II Bridge was added later, opening in 1991 to handle increasing traffic at the crossing.
Dartford Crossing Lacks Motorway Status
Because the crossing is an A-road, motorway rules do not automatically apply in the same way they do on the M25. National Highways consistently labels the crossing as the A282, including in announcements about closures and maintenance. This status is significant because the Dartford Crossing is the only fixed road crossing of the Thames east of Greater London, and keeping it as an all-purpose road provides a crossing option for road users and vehicle types that might be restricted on a motorway.
Where the Change Happens and How Busy It Is
On the Kent side, the M25 becomes the A282 around junction 2 near Dartford. The A282 has its own junctions, including 1a and 1b, before reaching the tunnels or the bridge. On the Essex side, it rejoins the M25 near junction 31 at Thurrock. For most drivers, the transition is smooth, and the crossing is commonly viewed as part of the M25 journey.
Despite being a short break in the motorway, the A282 is one of the busiest sections of the route. National Highways reports that more than 50 million vehicles use the Dartford Crossing each year. It was designed to handle around 135,000 vehicles per day but currently averages about 150,000, with peak days reaching as many as 180,000. Around 40 per cent of daily users are freight vehicles or HGVs. Northbound traffic uses the two tunnels under the Thames, while southbound traffic crosses the 137-metre-high Queen Elizabeth II Bridge.
Officially, the Dartford Crossing is not part of the M25. The motorway stops, the A282 carries traffic over the Thames, and the M25 resumes on the other side. This means any claim of driving a complete lap of the M25 technically includes a stretch on an A-road.
