In the last 12 months, the Dartford River Crossing (DRC) has seen more than 55 million vehicle crossings. This is 1.6 million (2.97%) more crossings than the previous 12 month period. In March 2017, a 15.75% increase in monthly crossings was recorded.
The crossing is designated Critical National Infrastructure (CNI). Crossing operator Connect Plus Services (CPS) is under pressure to keep traffic flowing through this aging asset.
The challenges at Dartford are myriad. The northbound tunnel bores, taking traffic from Kent into Essex, opened in 1963 (west) and 1980 (east). This makes them among the oldest of the 140,000 assets CPS looks after on behalf of Highways England.
A comprehensive and continual maintenance and renewal / upgrades schemes programme is necessary to keep the tunnels functioning requiring night-time closures throughout the year. In the event of a full northbound closure, the prescribed diversion route via the restricted Blackwall Tunnel also impacts these drivers, adding at least an hour to every journey.
CPS is continually looking for opportunities to provide better journeys for its customers.
In early June, complex electrical works were required to upgrade the back-up power system for the tunnel safety control systems. This required a full power down, rendering both of the tunnels out-of-action overnight. While planning the closures, CPS senior engineer Steve Dodds, and Dartford’s service delivery manager David Cook devised a way to keep traffic flowing in both directions.
The QEII Bridge, which carries southbound traffic from Essex into Kent is a four-lane carriageway. Crossover points north and south of the DRC allow traffic to be diverted between north- and southbound carriageways in emergency situations, with minimal intervention required to remove moveable Vehicle Restraint System (VRS). A contraflow arrangement across the bridge, with a lane running in each direction, would keep all traffic flowing.
Planning for the contraflow began in early 2017. CPS worked with Highways England and its traffic officer service to develop the original closure devised for the 2012 Olympics emergency response plan, but never used.
Highways England granted CPS exemption to work outside normal working hours, enabling deployment and removal of traffic management either side of a full shift of work.
CPS’ onsite incident support units, maintenance and recovery teams removed VRS and remained in strategic lay-up points. Deployment took around 2 hours, with traffic management lifted in less than 90 minutes.
The electrical works were planned in detail to ensure that the tunnels would be safe to open again by the next morning. With the support of CPS internal teams and our technology supply chain partners all systems were returned to full operation on time.
David Cook said “This first-ever deployment of a contraflow across the QEII Bridge was a positive result. Traffic flow remained steady, with minimal delay, in both directions.
“We have identified further improvements we can make to both the layout of the chicanes, and reinforcement of signs for drivers, but we are confident we have a plan for use in the future, both for emergency situations and planned maintenance.
“Ultimately, we have provided a better experience for the road user, by which we measure our greatest success.”
- East tunnel closed, allowing access to north and south crossover points. VRS removed
- Lanes 4, 3, 2 closed southbound over bridge, allowing access to both sides of bridge
- Lanes 1, 2, 3 closed northbound at Junction 1B
- Single lanes running in each direction
- Northbound traffic stopped under rolling road block and switched onto bridge (Lane 4)
- Southbound traffic running through Lane 1
- Lanes 2 and 3 used as buffer lanes
- Advisory 40mph limit southbound, 50mph northbound
- Traffic management removed using exact reversal of deployment process