New roundabout plans – your questions answered

After Melksham Independent News sent readers’ questions to Wiltshire Council about the proposed changes to Farmers Roundabout, they have responded with the following answers:-

It has been suggested that banning the right turn movement from the A350 into the Asda site might help traffic flows in the area. Has this been considered?

The Asda junction currently operates as an “all movements” facility, providing access to the supermarket and also a range of other retail outlets and distribution centres within the adjoining business area. The Asda junction not only caters for car traffic, but also for large HGVs and other vehicles operating from that site.

The removal of the right turn access into the Asda area was considered at an earlier stage of the scheme development, but was discounted for various reasons including:-

• Vehicles wishing to turn right into Asda would be forced to perform a U-turn manoeuvre at Farmers Roundabout, thereby adding to the high traffic flows at that location and exacerbating existing queues.

• The rerouted traffic would need to pass through several sets of traffic signals at Farmers Roundabout, thus increasing journey time for the re-routed vehicles as well as impinging upon other traffic already in the area. Simply put, the re-routing of Asda-bound traffic would diminish the traffic flow improvements that the scheme is seeking to bring forward.

• Given the layout of the existing junction, and the need to control the A350 northbound traffic to allow vehicles to leave Asda, the proposed scheme automatically provides opportunity for southbound traffic wanting to make a right turn.  This would be the case whether such a junction arrangement was used or otherwise, and so no delay is actually generated by a right turn movement at this location.

• In general terms, on busy sections of the network it is often preferable to allow vehicles to leave that network as soon as possible, rather than retaining them unduly on the road, causing further interactions and delays with other traffic.

Will the existing traffic signals at McDonald’s/Aldi be linked with those at Farmers Roundabout/ Asda/A365 Bath Road?

The emerging scheme does not include the McDonald’s/Aldi traffic signals to be linked with those included in this scheme.  The junctions at Farmers Roundabout, Asda and A365 Bath Road are all located in relatively close proximity, with the link distances between the junctions being around 130m – 150m.  Conversely, the McDonald’s/Aldi junction is relatively remote, with the link distance back to Bath Road being around 350m.

The distances between Farmers Roundabout, Asda and Bath Road junctions mean that traffic queues from one junction can impact on adjacent junctions and in this regard it is sensible that the opportunity is taken as part of the scheme to link these junctions through the proposed traffic signal layouts and configurations.  The distance between the McDonald’s / Aldi traffic signals and those at Bath Road is, however, sufficiently large that queuing from either junction does not have a significant effect on the other and as such, it is considered that there is no immediate need to provide such a connection.

To connect the McDonald’s/Aldi signals with those at Bath Road would require a new duct and cable to be installed throughout this length of carriageway, with associated additional traffic management, lane closures and road closures beyond those already needed as part of the scheme. It is likely that service diversions would be required in order to accommodate the new infrastructure, and the amount of services buried in the footway and highway along this section of the A350 is such that this would be disproportionately expensive, compared to the potential benefits it would provide.

Clearly, once the new scheme is put in place, the new traffic signal system, along with those at McDonalds/Aldi, will be monitored to ensure they operate as effectively as possible.

Why not build a bypass rather than spending money at Farmers Roundabout?

Proposals for an eastern bypass at Melksham are still at a very early stage of development, and currently there are no firm proposals. Many difficult hurdles and issues would need to be overcome before it became a reality – not least the availability of land, the construction of a new bridge across the River Avon, concerns regarding development within a flood plain, potential ecological and environmental concerns, the mechanism for delivery, planning considerations, and indeed the availability of funding.

The scheme at Farmers Roundabout has largely been funded by the Department for Transport’s National Productivity Investment Fund.  It is aimed at addressing the existing situation at Farmers Roundabout, which has for some time been recognised as experiencing high volumes of traffic in the peak periods, causing significant queuing and delays and unpredictable journey times.

The current secured funding is dedicated to, and is required to be spent in connection with, the existing situation at Farmers Roundabout. It is not possible to utilise these funds in connection with a wider project.

Are there any enhancements being made for cyclists and pedestrians as part of the scheme?

The focus of the project is very much aimed at improving the traffic (vehicular) capacity at Farmers Roundabout. Nevertheless, surveys have been undertaken as part of the design process to understand the current amount and nature of pedestrian and cycle movements through the junction, and to seek to make improvements where possible.

Surveys have shown that the number of pedestrians and cyclists passing through or seeking to cross the A350 at Farmers Roundabout is very low. It is anticipated that footway resurfacing works will be included in certain locations around Farmers Roundabout, and that there will be enhancements to the existing, and new dropped kerb crossing points provided.

Off-carriageway facilities for cyclists, which were implemented as part of previous developments in the area, already exist to the west of the junction and these will be retained. The new traffic light system at Farmers Roundabout is designed to provide greater control and certainty regarding vehicle movements at the junction, and this should help all users, including cyclists, more readily negotiate the network.

Will the traffic signal timings adjust during the day and will the system incorporate the latest technology and react to traffic conditions?

Yes. The new traffic signals at Farmers Roundabout will operate using MOVA (Microprocessor Optimised Vehicle Actuation), and will be linked to the traffic signals at both the Asda and A365 Bath Road junctions. The MOVA system monitors traffic queue length build up through detectors either installed in the carriageway surface, or mounted on top of signal heads. Operating parameters such as maximum permissible queue lengths before the lights change, the priority of certain movements based on max queue length, and longest and shortest permitted green/red light times then allow the MOVA system to optimise the junction capacity.

The MOVA system will also cover the Asda and A365 Bath Road junctions.

As part of the installation process, traffic signal engineers will set the configurations and operating parameters of the system such that MOVA can then respond to changing traffic conditions throughout the day.

Could the new traffic signals be set to operate during peak times only?

The use of part-time traffic signals is becoming much less frequent on highway networks. In the past, they were generally used on motorway junctions, which tend to be relatively ‘stand-alone’ locations. However there have been suggestions that part-time operation can contribute to driver confusion and subsequent safety concerns, with the stop line indicating one thing to the driver, but the non-operational signal heads suggesting something different.

The close proximity of the Farmers Roundabout junction to the other signals at Asda and A365, which operate 24/7, means that the introduction of part-time use is not viable. Nor is it considered to be a safe solution given the confusion that can develop.