Hambrook lights traffic restrictions

Background

A national assessment of local authority roads by Defra (Department for Environment, Food & Rural Affairs) in 2017 identified the A4174 ring road, between the M32 Junction 1 and the Bromley Heath roundabouts, as being above the roadside nitrogen dioxide annual mean limit of 40 µg/m3 (microgrammes per cubic metre).

We were required by the government in 2018 to assess and introduce actions that could help reduce nitrogen dioxide levels to meet the legal limits in the shortest time possible.

Changes to the Hambrook junction

The following changes were implemented to the junction in 2019:

• changing the westbound bus lane to an all-traffic lane through the junction to the M32 traffic signals
• removal of the right turn onto the B4058 from the westbound carriageway of the A4174 ring road
• removal of the straight on movement for the B4058 northbound from Frenchay
• removal of the right turn from the B4058 from Frenchay onto the A4174

There are no changes to the direction of travel southbound on the B4058 from Winterbourne.

Impact of the changes

Journey times for some routes are slightly longer as drivers need to go around the M32 roundabout to access the B4058 northbound, and/or the ring road from Frenchay. To offset this, changing the bus lane to an all-traffic lane improves westbound capacity.

Reducing the time vehicles are stationary at the traffic lights and allowing ring road traffic to flow more efficiently, should reduce emissions and improve air quality.

Badminton Road M4 overbridge closure

The sudden closure of the National Highways M4 overbridge has impacted the surrounding road network including the Hambrook junction.

Similar restrictions were implemented at the Hambrook junction during the major repairs to Bromley Heath Viaduct a few years earlier, which helped the flow of traffic.

Air quality monitoring and assessment

We are continually monitoring the air quality at Hambrook. We are required to supply two consecutive years of compliant monitoring data to the Joint Air Quality Unit, which show the roadside nitrogen dioxide levels are within the legal limit (40 µg/m3). The government’s Joint Air Quality Unit (JAQU) was established by Defra and the Department for Transport to deliver the national nitrogen dioxide reduction strategies.

It took longer than expected to obtain the required data due to the Covid-19 pandemic. Data gathered for 2020 and 2021 was not typical and was not accepted as representative of normal conditions.

Recent monitoring data has shown significant improvements in the roadside nitrogen dioxide levels between the M32 and Bromley Heath roundabouts.

We have submitted data for 2022 and 2023 to JAQU. The results of this assessment are due later in 2024 and we will the publish the report when it is available. We cannot review the restrictions, until this is shared with us.

In addition, we will need to demonstrate that nitrogen dioxide levels will not increase in the future with or without the restrictions in place.

Why we need to improve air quality

Air pollution is a significant public health issue.

Poor air quality has a number of adverse effects on health and is recognised as a contributing factor in the onset of heart disease and cancer. It particularly affects children and older people, and people already suffering from respiratory and cardiovascular conditions.

The UK has legislation to ensure that certain standards of air quality are met to protect health, but in some areas the standards have not been met.

The most immediate air quality challenge faced both at a national and local level is to meet the standards for the pollutant nitrogen dioxide (NO2). This type of pollution is largely caused by vehicle emissions, with road traffic contributing about 80% of the NO2 pollution around roads.