Skip to main content

Hambrook Air Quality Action

We have implemented an Experimental Traffic Order (ETO) restricting some vehicle movements at the Hambrook traffic lights. This follows a government directive to improve air quality on this part of the A4174 ring road in the shortest time possible for all road users including motorists, bus passengers, cyclists and pedestrians.

An ETO is a trial which can be in place for a period up to 18 months, during which time consideration is given to making the order permanent. Orders are subject to a statutory process which allows the public to comment formally and provide feedback.

Complete questionnaire

More information about the consultation is available here, however comments will only be accepted when the restrictions at Hambrook are implemented on Sunday 11 August 2019.

Changes to traffic movements at the Hambrook lights

The Experimental Traffic Order currently in place at Hambrook restricts a number of movements.

These are:

  • removing the westbound bus lane through the junction to the M32 traffic signals
  • removing the right turn facility onto the B4058 from the westbound carriageway of the A4174 ring road
  • removing the straight on movement for the B4058 northbound from Frenchay
  • removing the right turn facility from the B4058 from Frenchay onto the A4174

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

We do understand that these changes will make some journeys slightly longer as drivers will be required to drive around the M32 roundabout in order to access the B4058 northbound and or the ring road from Frenchay. We apologise for the inconvenience caused.


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 the most vulnerable in society; 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.

South Gloucestershire

A national assessment of local authority roads identified the A4174 ring road between the M32 Junction 1 and the Bromley Heath roundabouts as being above the annual mean limit value for NO2 of 40 μg/m3 (micrograms per cubic metre). This is the only road in South Gloucestershire predicted to exceed these limits in this assessment.

The council was required by government to assess if there were any actions that could be taken to reduce the high NO2 levels on this section of the ring road to meet the legal limits in the shortest time possible.

Traffic modelling video showing changes to the Hambrook junction

The video shows the changes in the am and pm peak if we don’t make any changes (on the left) and if we do make changes (on the right). The changes to be implemented over the 10-11 August include the removal of the westbound right-turn to B4058 Bristol Road to Winterbourne and of the northbound B4058 Bristol Road right-turn to A4174 and straight on movement to Hambrook from Frenchay at the A4174 Hambrook crossroads. Instead this traffic will either head west along the A4174 and turn at the M32 Junction 1 roundabout to head eastbound, then turn left at the Hambrook junction, or use an alternative route away from Hambrook Junction.

This modelling will be tested through the Experimental Traffic Order and the restrictions will allow east and westbound traffic on the ring road to flow more efficiently, thereby reducing NO2 emissions. This section of road could become compliant with the limit sooner than predicted, bringing with it all the health benefits of better air quality.


Modelling shows that reducing the amount of time and number of vehicles that are stationary at the traffic lights will reduce NO2 emissions and should improve air quality. However, this is a trial and we will not know if the scheme has successfully reduced air pollution and to what level, until all the data has been collected and analysed.

South Gloucestershire already has Air Quality Management Areas (AQMAs) in the Kingswood and Warmley area and also Staple Hill where the NO2 levels are above the national target of 40 µg/m3 (micrograms per cubic metre). We have an action plan to improve the air quality in these areas as required by UK legislation in the Environment Act 1995.

However, the UK government has the responsibility of meeting the legal limits set by the European Union (EU). The EU limit values largely mirror the national targets although there are some differences in where the standards apply. The government carry out national air quality assessments using computer modelling and some monitoring to compare NO2 concentrations with the EU limit values. This has identified more roadside locations in the UK with NO2 levels above the maximum limits, in addition to the AQMAs already declared by local authorities.

In response to this, the government produced a UK plan for tackling roadside NO2 concentrations in July 2017, followed by a further supplement to the UK plan in October 2018. This plan resulted in local authorities being directed to reduce roadside NO2 concentrations to comply with the EU limit value (40 µg/m3) in the shortest time possible.

The changes are designed to reduce the amount of time vehicles are stationary at the lights not to increase the overall amount of traffic on the road. More traffic will be able to pass through the junction on the A4174 for a given time period as a consequence of the changes. Movements are being restricted so some phases of the traffic lights sequencing will be removed.

The trial measures now proposed at Hambrook crossroads are in line with the arrangements put in place during the Bromley Heath viaduct works. As a result of that experience we are confident that there will be traffic flow benefits to the ring road. The aim of the trial is to confirm and quantify the benefits under more usual traffic conditions.

There are no planned changes to the sequencing at the Bromley Heath roundabout. To do so would attract increased volumes of traffic and undermine the traffic flow benefits being sought.

The road works required to install the measures will take approximately one weekend and are proposed to be carried out on 10 and 11 August 2019.

No, we do not need to implement a closure of the A4174 ring road. Lane closures will be in place while the changes are put in place over the weekend of 10 and 11 August 2019. Further details of lane closures will be publicised online and with road signs.

As an Experimental Traffic Order, there will be an 18-month period to assess and monitor the changes and make the changes permanent (if that is what we decide to do). Once the trial restrictions are implemented, over the weekend of 10 and 11 August, you will then be able to submit formal comments. Comments may be made via our consultation webpage and include any grounds for objection to it being made permanent.

The consultation page is available here although comments will not be accepted until the changes are implemented in August. Members of the public will be able to comment during the first six months of the trial.

The next six months will be used to collate and analyse the responses, and analyse air quality data received over this period. The final six months will be used to decide what we are going to do and, if we decide to make the changes permanent, to complete the legal process.

The Experimental Traffic Order will run for up to 18 months. Variations of the order are possible for the first 12 months of the order, after which consideration will be given to whether the restrictions should be made permanent or not.

We will keep people informed of the process and any decisions made during the Experimental Traffic Order period.

Improvements to traffic flow along the ring road will bring more reliable journey times to the services that pass along this section of the A4174 including the m3 and m3x services.  Presently congestion can prevent access to the A4174 westbound bus lane through the crossroads rendering it ineffective.  By removing the bus lane for the trial there is potential to move vehicles more efficiently through the junction and so improve journey times for all westbound traffic, including bus services.

Bus services using the B4058 Bristol Road will be affected by restrictions too. We are liaising with bus operators to limit the impact on routes affected and will publicise any changes to services before the order is implemented in August.

Routes affected

  • 19/19A Cribbs Causeway to Bath
  • Y4 Bristol to Yate

Yes, this is the only scheme of its type we are currently proposing and follows a government direction to improve air quality at this location. We are implementing this scheme with the aim of complying with the annual mean limit value of 40 µg/m3 for the pollutant NO2 in the shortest time possible.

We have been monitoring NO2 levels where people live near this junction for some years. The results show that the levels here are within the national limits for where people live. This is mainly because the houses are set back from the road and pollutant concentrations quickly drop off with increasing distance from the roadside.

Additional monitoring has been set up at the roadside for the purposes of the trial to monitor the impact of the traffic restrictions at the junction. Our annual air quality reports, which include the monitoring results, can be found on our website here –

The existing traffic signal controlled crossings for cyclists and pedestrians will not change throughout the trial. We will provide cyclists direct access to the triangular island through the new barrier if you are approaching on the Bristol Road from Frenchay direction only.

With that one exception, the short sections of road through the traffic islands will be blocked off to everyone and so when cycling north you will not be able to use those sections to go right across in one go on the road from Frenchay. You will be expected to use the crossing from the triangular island for safety reasons as it would be unsafe to join the left turn from the A4174 ring road towards Winterbourne.

We are working with Highways England which manages the M32 motorway including the set of traffic signals at the top of the entry slip road. Those traffic signals control peak period ‘ramp metering’ which holds traffic back from joining the motorway and it has been agreed this system will not be used during our trial.

By suspending the ring road bus lane there is extra space created for other vehicles to occupy and this will help reduce congestion.

We will be starting the trial at a time of year (August) when traffic volume is at its lowest. We will be monitoring traffic throughout and our early observations will be used to further refine the traffic signal operation of the Hambrook lights and Bromley Heath and M32 roundabouts if necessary before traffic levels traditionally increase in September.

Although additional traffic is generated by local development, this section of road is affected by traffic from a much wider area and is a very important link to the motorway network. Increased demand for use of this road reflects the general growth and prosperity of our region. Whilst new vehicle emissions are improving all the time, the increasing number of journeys being made is undermining the rate of improvement that might be seen here.

You can view updates on our consultation page and on this webpage. We will also keep our StreetCare Facebook updated with information about this Experimental Traffic Order.

Like our page at

To contact the team please call 01454 868000 or email




Is there anything wrong with this page?