Highways England is digging deep to prepare for improvements to a vital East Anglia junction, with preparatory works starting at the A47-A11 Thickthorn Interchange.
Highways England is improving the A47 in six places between Peterborough and Great Yarmouth as part of a £450 million-plus investment, including the Thickthorn Interchange with the A11 at Norwich.
Ground investigation works have begun with five holes being gradually drilled up to 120 feet deep to help the project team to understand the existing rock and soil types, which will inform their work to improve the junction.
Once the works are completed, the upgraded junction will see journey times improved by between four and five minutes for the 53,000 drivers who use the roundabout on a daily basis, while making the junction safer by reducing the number of accidents.
Highways England programme lead for the A47, Chris Griffin, said: “The Thickthorn Interchange connects the A11 to the A47, enabling the growing economic activity around Norwich. The current junction can act as a bottleneck for those who use the roundabout daily, causing queues and slowing journeys. Our improvements to enlarge the roundabout and provide dedicated free-flow links will reduce delays at the junction, ensuring smoother and safer journeys.”
The work will see a 17-foot-long drill being used to gain a better understanding of the ground conditions, which is vital before work can start on the upgrade. Noisy work will only take place during the day, with Cantley Lane South currently closed from the A47 to the railway bridge until Friday 9 July with a clearly signed diversion route in place. One lane is currently closed on the A11 approaching Thickthorn from 8pm to 5.30am on weekdays. Further survey work will continue until October, although no further closures are planned.
The teams will be drilling around 30 feet per day, looking at what lies beneath the road surface. Up to a metre down into the ground of the area is man-made, with the project team needing to understand what types of soil, rock and groundwater are in the area so they can build the roundabout upgrade swiftly and efficiently.
Highways England announced its preferred option for upgrading the Thickthorn junction in August 2017. Since then, plans have been refined based on feedback from the consultation, with the latest designs shared with road users a year ago.
The latest changes see the previously proposed A47 westbound to A11 southbound free-flow link road replaced with a dedicated free-flow left turn lane at the roundabout, reducing the environmental impact of the proposed scheme while still improving journey times. Traffic lights will be installed on the B1172 arm of the Thickthorn roundabout, while a fourth lane will be added to the southern half of the roundabout. The B1172 will also have a reduced speed limit of 40mph between the junction and Hethersett, improving safety. Existing junctions to and from Cantley Lane South to the A11 and A47 will be closed, and replaced with better, safer access via a bridge over the A11 to the B1172.
A footbridge for pedestrians, cyclists and horses has moved closer to its original position, reducing the journey time and providing a safe dedicated crossing of the A47 for those users. The option selected will see a new, free-flowing link road created for drivers heading from the northbound A11 to the eastbound A47. The link road will allow drivers to avoid using the roundabout, which itself will be freed up for drivers making other turns at the junction.
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