M25 and A282

Officially named the London Orbital, nicknamed the "Road to Hell", and frequently derided as nothing more than a very big car park, this is London's outermost collar and one of the world's biggest ring roads. It could only be the notorious M25.

Despite all the hype, the M25 isn't even a full circle. The Dartford Crossing (comprising the Dartford Tunnels and the Queen Elizabeth II Bridge) over the Thames in the east and its approach roads are designated A282, because the first Tunnel was built in the 1960s as a local connection. A second tunnel was added, and because it was a dual carriageway, 1980s planners considered it eminently suitable for routing the M25 through. It remained A282 nonetheless, and has since been adorned with a bridge to double its capacity.

It's not just the biggest ring road in the world, it has other accolades. For example, consider the fact that this was the most expensive motorway Britain ever built, costing £909m at 1986 prices, or roughly £7.5m per mile. Since then it's had many times that amount of money spent on widening and other improvement works.

Since its opening in 1986, it hasn't exactly been cheap to maintain, with a cable stayed bridge to double up capacity at Dartford, countless widening schemes and now expensive things like Variable Speed Limits in desperate attempts to keep traffic moving.

The eternal question is: why is a simple ring road, a 360-degree bypass of a city, so badly congested? There appear to be three principal reasons. First, as a sweetener to locals along the route, junctions were dropped in all over the place. They allowed the road to be built, but allowed lots of local traffic onto what was intended as a long-distance route. It also means the road is now used by many commuters.

Second, it was meant to be the outermost of three or four ring roads for London (for which see the Ringways feature); not counting the inner ring road and South Circular, which are signed routes along city streets, it is currently the outermost of one and a half ring roads.

Thirdly, and partly for the reasons above, the demand for this road was so grossly underestimated that when it was finally completed in 1986, it was already out of date. Demand outstripped capacity within a few short years and ever since then it's been a long and expensive battle to make things move once more.

Tolls

The Dartford Crossing on the A282 between M25 junctions 31 and 1A is subject to a congestion charge. The road is monitored by cameras with automatic number plate recognition technology and all traffic using this road between 06:00 and 22:00 is liable to pay the charge. There are no toll booths or collection facilities on the road itself. The charge can only be paid online, by phone, or by setting up an account (which includes a small discount).

The prices above are intended as a guide only, and were correct at 10 April 2015. Please check the official website for up-to-date charges.

The charge can be paid online at the Dartford Crossing website, by phone on 0300 300 0120, or by setting up a Dart Charge account.