"The relevance of historical data is that M4 traffic volumes were even higher prior to 2010 than they were in 2019, let alone now."I'd admit past data is relevant to an extent but not predictive. I don't know what data point you are looking at but the one I am using is Site number: 46121 which is just to the east of Hogarth Roundabout. This shows that with a few outliers, the number of vehicles passing this point on a daily basis is between around 85,000 and 110,000.It is not correct to say that there were higher occurrences at the beginning of the century than we have seen in recent years. The peak was 2018 followed by 2019 which also happen to be the peak years for Heathrow passenger numbers. The monthly Heathrow numbers indicate that the 2018 record year will be substantially exceeded in 2024. Past data suggests that this will be accompanied by a similar increase in traffic on the A4."HGVs only make up about 3% of vehicles on the M4, the overwhelming majority are cars, so even if HGV volumes doubled, traffic would still be less than it was in 2019 and a lot less than it was in the 00s."There is a confusion here between 'traffic' and the number of vehicles on the road. HGVs take up much more road space and combine that with the significant increase in car size, the same number of vehicles that used the road in the 00s will cause a lot more congestion in 2024.My concern is that if you combine the Heathrow resurgence, with the lessening of the dampening effect of ULEZ as people switch to compliant cars and the significant growth in housing units along this corridor (28,000 in Hounslow borough alone) we will see the number of motor vehicles on the A4 go beyond the historic range.Mark is right that better public transport can help and there may be some forces that create an equilibrium here that prevent vehicle number rising above a certain amount. However, TfL don't seem to believe this which is why they want to widen the A4.
Jeremy Parkinson ● 4d