A £7.5m junction project by South Tyneside Council has delivered a 36% reduction in casualties since it opened in July last year as well as improving flood resilience and journey times, reliability and queue lengths. David Pringle, project manager at South Tyneside Council, explains how.
Lindisfarne corridor in South Tyneside is a key part of the strategic highway network and is formed by the Lindisfarne Roundabout at the A19/A194 and the John Reid Road roundabout at the A194/A1300.
The corridor is heavily used by the commuter traffic flowing eastbound and westbound to key employment sites inside the borough and to those in neighbouring authorities, and also to access the A19 trunk road for longer commuting journeys.
The Lindisfarne Junction was of concern for a number of reasons including traffic congestion, localised flooding, ‘rat-running’ through adjacent estates and air quality. In addition, there had been several occasions where the junction had flooded following severe weather, leading to congestion around the greater road network. The corridor was also designated an air quality management area by Defra in 2017.
Several options were designed and modelled for South Tyneside Council. The council chose a solution that addressed all these issues.
In order to decrease congestion, the Lindisfarne Roundabout, as well as the corridor itself, was widened to include an additional lane in all directions.
John Reid Road roundabout was partially widened as required. Existing trees, which had to be removed to facilitate the widening, have been replaced on the remaining corridor to reinstate the noise and visual benefit previously enjoyed by the residents.
Additional space to facilitate the extra lane on the Lindisfarne roundabout was gained by a slight reduction in the diameter of the roundabout containing the embankment supporting the A19. Additional filter drainage as well as embankment strengthening works (replacement of existing fill with 6F5 granular fill) was adopted to allow the toe to be brought in, and the slope of the embankment to be increased, without compromising the trunk road above.
These widening works have enabled provision of a dedicated right-turn onto the A19 northbound on slip and the widening of this to two lanes provided stacking without compromising the westbound traffic previously blocked from proceeding by vehicles waiting to take the A19 slip.
This has also reduced rear end shunts by vehicles changing lanes. Additional stacking has been provided on all approaches which has contributed to better traffic movement.
In order to reduce the flooding problem and make the strategic and local road network more resilient and reliable at the Lindisfarne roundabout, a storm water attenuation system has been introduced.
This 1150 cubic metre volume ‘Tubosider’ type tank has been located within the adjacent King George playing fields to the north-west. It was necessary to introduce a bespoke horizontal inlet gully to cope with volumes of water being removed from the roundabout during a one in 100 year storm.
This gully, which is set behind the running line of roundabout, discharges via gravity into the tank via an 825mm diameter pipe. Due to a limit on discharge volume allowed into the local river Don (5l/sec) the tank is discharged via a pumped system back into the highway drainage system (20l/sec). A further measure has been added in the shape of an overflow, which will discharge onto the field area in the event of exceedance of the tank capacity.
The spoil generated by the installation of the tank was retained on site and used to greatly improve the football field facilities for the benefit of the local community.
In addition to the scheme having the benefit of significantly reducing congestion and journey times, this in turn has generated an improvement in air quality to ensure this complies for NO2 emissions. This was due to quicker and more efficient movement of traffic through the corridor, as well as reduced times when vehicles are standing stationary and the incidence of stop start manoeuvres.
The introduction of an enhanced crossing point in the form of a Toucan crossing, in conjunction with the existing footbridge facility, has seen improved safety for non-motorised users (NMUs) travelling between the estates, an increasingly important factor due to the location of schools.
The introduction of a bus gate from the adjacent Scotch Estate has resulted in a vast reduction in the number of ‘rat-runners’ using the route, which has increased safety on the estate as well as reducing conflicting manoeuvres on the A194 west bound carriageway.
The decision to allow buses, as opposed to a total closure, was based on the limited number of services egressing from the estate per hour and the fact that they did not need to cross out of the nearside lane in front of increased volume of oncoming traffic. These improvements have resulted safer routes for NMUs and a safer environment within the estate, as well as a reduction of 36% in road traffic casualties*.
The scheme, which was designed by AECOM, delivered by Galliford Try and jointly funded by the Local Government Fund (£6.1m via the North East Local Enterprise Partnership and South Tyneside Council £1.4m), was completed on time and within budget and has since received a commendation at the regional Institution of Civli Engineers Robert Stephenson Awards.
Cllr Mark Walsh, lead member for housing and transport on South Tyneside Council, said: 'Lindisfarne was the first of a wider programme of strategic transport investment projects that aim to help reduce congestion and establish a strategic gateway into South Tyneside and we’re delighted with its success.
'Schemes such as this are futureproofing our road network by developing infrastructure to accommodate upcoming developments and reinforcing the economic potential of the A19.'
*Source: TADU (Traffic Accident Data Unit) which is a regional database for Tyne and Wear authorities