The Dartford Crossing (the A282) has become one of the most strategically important parts of the UK road network, carrying traffic of national and international importance, as well as catering for regional and local journeys. It is the only river crossing on the strategic road network to the east of London.
The Dartford Crossing (A282) is not built to modern motorway standards. The crossing comprises two, two-lane tunnels northbound, and the The Queen Elizabeth II Bridge, opened in 1991 carrying four lanes of southbound traffic.
The northbound tunnels are aged and relatively small by modern standards, such that for safety reasons, abnormal and hazardous loads have to be escorted through them while all other traffic is held back.
Traffic lights at the Dartford Tunnel bring traffic to a standstill on average 100 times a day by a small number of oversized & hazardous goods vehicles which need to be escorted through the tunnel, in a convoy.
Each convoy can take up to 2.5 mins to travel through the tunnel, and a tunnel is closed around every 15 mins.
This is believed to be one of the primary causes of northbound congestion, which can streatch back some six miles or more. This congestion is also thought to be the part of the cause of secondary accidents, which cause further hold-ups.
The southbound bridge has a fixed 50mph speed limit imposed, again for safety reason and this limit is often lowered using the Variable Speed Limit signs in windy conditions. The bridge is often closed completely in severe weather.
Therefore it is considered that the Dartford Crossing a missing link, a bottleneck in probably THE most important links in the UK Strategic Road Network.
The crossing is the busiest in the United Kingdom. As of 2014/15, the crossing operates at a capacity of 137,411 average vehicles per day (avpd) and in practice the crossing carries as much as 160,000 vehicles per day. This exceeds it’s design capacity of 135,000 avpd. There is clearly insufficient capacity to cater for current and future traffic demand. Because the design capacity has been exceeded, the crossing is subject to major traffic congestion and disruption, particularly when parts are closed because of accidents or bad weather.
Note that 40% of the traffic using the existing crossing is classed as National, i.e. travelling from south of junction 2 to north of junction 30 or vice-versa. The diagram on the right is taken from Scheme Assessment Report Volume 2.
For more information please read Section 2, on page 2 of Pre-Consultation Scheme Assessment Report Volume 1: Executive Summary.
Figures show the Dartford crossing has been at least part-closed once every three days in the year to March 2016.
Summary of closures (in 1 year):
Total number: 108
Number of complete closures: 1
Closures for planned construction or maintenance works: 81
Unplanned bridge closures: 9
Unplanned closures of the west tunnel: 5
Unplanned closures of the east tunnel: 12
It was also revealed that the average incident at the crossing takes 27 minutes to be dealt with, but then up to five hours for roads to then return back to normal following a build-up of traffic.