A key junction on the outskirts of Bristol will remain restricted as, over a two-year period, the air quality data was not found to have been consistently within the legal limit. The Hambrook junction, which includes the A4174 between the M32 and the Bromley Heath roundabout, and the B4058, was restricted in 2019 as a result of high nitrogen dioxide levels.
South Gloucestershire Council recently confirmed that data regarding air quality was submitted for 2022 and 2023. In order for the restrictions to be reviewed, there would need to be two consecutive years of compliance where the nitrogen dioxide levels are below the legal limit.
The government’s Joint Air Quality Unit (JAQU) has found that nitrogen dioxide levels were acceptable in 2023, but that in 2022 not all the data was at the recommended level. It means that the junction, which has proved controversial with motorists, will remain restricted for the foreseeable future.
What restrictions were placed on the Hambrook junction?
In 2017, nitrogen dioxide readings were above the annual mean limit value and due to government requirements, traffic restrictions were implemented in 2019. This resulted in part of the junction being blocked off and traffic being diverted.
The changes affected the B4058 heading northbound from Frenchay, where the right-hand turn onto the A4174 and the straight-ahead route (towards Winterbourne via the B4058) was removed. The only way traffic could go was on the A4174 westbound towards the M32, which was facilitated by an extended left-turn lane to create two left-turn lanes.
The A4174 westbound also saw its right-hand turn, onto the B4058 towards Winterbourne, blocked off. The bus lane was suspended creating an additional traffic lane.
Originally, the scheme was planned for 18 months. However, it remains in place six years on.
Why was the scheme so controversial?
The scheme, since its implementation six years ago, has proved to be controversial for motorists. Journey times for some routes, in particular those travelling from Frenchay, were increased as drivers would need to travel to the M32, go round the roundabout and back up the A4174 to access the northbound B4058 or the ring road.
The closure of the A432 Badminton Road bridge, which will be demolished next month, also led to increased traffic around the Hambrook junction. Thousands of people signed a petition calling for the scheme to be scrapped, in May 2024, as a result of longer queues and journey times.
Those who campaigned for the scheme to be scrapped also called out an apparent lack of progress that was being made in improving air quality at the junction. The council said at the time that no changes could be made to the junction until air quality data showed that nitrogen dioxide levels were at an acceptable level.
What has happened to nitrogen dioxide levels?
In 2023, nitrogen dioxide levels at the roadside were at an acceptable level. But, not all of the 2022 data was shown to be at a legal level, meaning that restrictions can not be lifted at this time.
The JAQU report showed that at two locations along the junction, both of which are located between the M32 and B4058, nitrogen dioxide levels were above the safe limit. In addition, three sites were at risk of exceeding the legal limit.
Data was also taken during 2020 and 2021, but due to the Covid-19 pandemic, the data was “not typical and was not accepted”.
In a Highways Update email, South Gloucestershire Council said: “The latest available Hambrook monitoring data has been assessed by the government’s JAQU.
“The JAQU report confirms the 2023 roadside nitrogen dioxide levels were compliant with the legal limit. However not all 2022 data was at the recommended levels.
“Unfortunately we cannot review the restrictions at Hambrook until we achieve two consecutive years of compliance. The 2024 data will be assessed by JAQU during 2025.”
What will happen to the junction once air quality improves?
In December 2024, before the air quality data results for 2022 and 2023 were revealed and when announcing a major project to improve the ring road, South Gloucestershire Council said: “This junction is still being monitored by the JAQU and therefore no changes can be implemented at this junction.
“Earlier proposals for a new bus gate at this site have been removed from the scheme as a result of this, however tie-ins will be implemented on either side of the junction.”
Bristol Live asked South Gloucestershire Council about what plans would be considered for the junction once the air quality data is within the legal limit for two consecutive years. The council said: “We will be considering all options within any measures that may or may not be imposed to maintain long-term compliance. At the appropriate point in time, all practicable options will be assessed.”