Ken Skates AM, Minister for Economy and Transport
I am writing to update members on congestion problems that were experienced on the M4 near junction 28 on 12 February.
It has been confirmed that the problems occurred due to a software problem with the signal sequencing at the Bassaleg interchange. During normal operation at quiet traffic times, the system moves into what is called remission mode to clear unwanted data. It should then return to the normal operating mode. However, on this occasion the system became locked into the remission mode. Siemens corrected the fault by 1pm that day and it has been referred to the engineering team to review the problem. In the meantime, Siemens will remain available and ready to respond to any further incidents.
The project team are also aware that prior to this incident there was an on-going issue with regards to traffic queuing southbound in the morning peak on the A467 (Forge Road). Following the opening of the new roundabout Costain undertook an initial traffic survey in December, 2018. The results were interrogated and minor changes introduced to traffic signal timings. Unfortunately this has not addressed the issue with traffic continuing to queue on the southbound arm of the A467 in the AM peak.
The project team have reviewed options to resolve the queuing. As a result they are now developing a more extensive package of traffic survey work in order to validate the pre-construction traffic flows. It is programmed to undertake these surveys in early March 2019, in order to comply with traffic survey data capture best practice.
Once analysed this traffic data will give the designers a greater understanding of the traffic flows, congestion and actual driver manoeuvres to inform any adjustment to the traffic signals and/or road layout arrangements.
We are very appreciative of people’s patience whilst this work is on-going.