CS9, air quality and congestion
There are an awful lot of posts and discussions about air quality in general and CS9 and its impact. Over the last year Michael and Tom seem to have posted numerous times about both topics and to clearly link them. Tom posted the other day that he never said CS9 will improve air quality, but that it won’t make it worse. However, a quick google search brings up articles by Hounslow cycling and others that seem to explicitly link CS9 with better air quality. We regularly hear how cycling reduces pollution, but not what the aggregate impact of measures like CS9 are.We can all agree we want cleaner air, hopefully the ULEZ will help though it seems a very large proportion of vehicles are compliant already. But the detailed air quality modelling for CS9 did not expect CS9 itself to improve air quality. The official report on air quality was very clear about this. The following is a direct quote from the summary of the air quality report:‘Overall, as there are both improvements and deteriorations in NO2, and negligible changes in particulates, these effects are collectively considered to be balanced and overall not significant.’But the report findings also build in an improvement in overall background pollution (regardless of CS9):‘By the scheme opening year of 2021, concentrations are lower due to improvements in background pollution and lower emissions from newer vehicle fleet. ‘So to be 100% clear, TFL based on ‘normal’ traffic patterns, did not expect CS9 to improve air quality. In fact, the previous quote logically implies pollution would be better without CS9, though likely not much. It was though expected that there would be winners and losers, as I posted in another thread. Winners include those on Wellesley Road, losers those living near the A4 and roads west of Hammersmith.There was also extensive traffic modelling undertaken by TFL that fed into the air quality report and was referenced in various documents and responses by TFL. Here are some extracts:‘Our traffic modelling previously undertaken for the proposals showed that any displacement of traffic would likely occur away from the A315 towards the A4. Updated traffic modelling shows during the evening (PM) peak, westbound traffic is predicted to reroute westbound onto the A4 as an alternative to Wellesley Road. Traffic would also reroute from the northern side of Hammersmith Gyratory, including Beadon Road onto Shepherds Bush Road in the morning (AM) peak. No access to the South Circular from Wellesley Road and from Stile Hall Gardens is predicted to reduce traffic in the westbound direction on Chiswick High Road and Wellesley Road while traffic would reroute partly via Oxford Road northbound and then Chiswick Roundabout’.‘The reason for the increases [in pollution] at these receptors is due to predicted increases in traffic by 9% as a result of the proposed scheme along A219 Shepherds Bush Road and a 3% increase in vehicles using A3220’.‘Traffic flows on the Hogarth Lane section of the A4 to the west of Hogarth Roundabout are predicted to increase by 5% as a result of the proposed scheme resulting in more than 5,000 vehicles using this section of road per day.’So not surprisingly, there will be displaced traffic, and it’s not clear what modelling TFL undertook to see the knock-on effect of that. For example, 5,000 more vehicles on the A4 west of the Hogarth is a lot, on a very congested road. The Hogarth roundabout is at capacity even now at peak times with the competing traffic flows (which will increase further with the GP LTNs, which were not included in the modelling). Remember when Tom shares data claiming that bike lanes do not increase congestion, he is referencing the roads with cycle lanes themselves, where traffic is often carefully controlled. But from the above we see TFL expecting significant displaced traffic. But the impact of this for example on the A4 or Hogarth roundabout is not measured.There is then the broader point. All the modelling was done based on ‘normal’ traffic and also the full version of CS9. The key stretch through central Chiswick is a ‘temporary’ version (though no funding is in place to upgrade this). This materially reduces capacity through central Chiswick and loses more length of bus lanes than the full version. This is well shown by TFL’s decision to include a new bus gate to the west before Acton Lane, which is designed to throttle back traffic from the central stretch (as clearly acknowledged by TFL). The fact in doing so, the bus gate divers traffic onto residential roads and part of CS9, seems to be a price TFL and the supporters are willing to pay. There has already been one serious accident with traffic diverting off CHR.Where does this leave us? I am sure 99% of us care about air quality and want cleaner air, we all breathe it. But at present, the temporary CS9 and the new LTNs/ road closure push even more traffic onto already busy and congested roads, the very places that currently have the worst air. This is not OK. Nor is diverting traffic including vans and large lorries onto residential streets to make the temporary CS9 work through central Chiswick. And most of all it does not put public transport first, which in my humble view has the be central part of any cleaner air strategy.We are also still in partial lockdown and it is hard to see the next year clearly. We can all hope that in a year or so, life will be back largely to normal. That needs big crowds at football, including the new Brentford stadium (couple of thousand cars expected in W4 for every match as a result), LHR operating well above it’s current 10-15% of passenger numbers, restaurants, shops and cinemas all open. All of which generate lots of traffic.So of course today, air quality has improved in the middle of a pandemic. Vehicle counts fell in 2020 and remain down in 2021 (remember that the number of vehicles on a road and congestion are very different things, but are often used interchangeably). What we can all agree on is its very hard to make predictions of longer-term effects from what we see today, no matter how much we analyse data and seek to infer causality into statistical correlations (or coincidences).I do not pretend to have all or even a few of the answers. But nor do the regular posters on here for whom cycling is a way of life as much as a travel choice. The streets and air belong to all of us, and most of us are drivers, pedestrians, public transport users and cyclists at various times of the week or day. Others have health or other challenges that may make them more dependent on public transport or cars/ vehicles. For central Chiswick this should mean a council that engages with and allows key decisions to be led by local business, as part of a comprehensive town centre strategy. This needs the FULL consultation of all these businesses as well as ALL local community groups. Perhaps our local councillors can take the lead in ensuring the current Chiswick Shops Task Force is led by business and as inclusive to all groups as possible. Maybe we can all agree that public transport is front and centre, and we demand accessible step free access to the tubes in W4, as well as asking why tube and bus fares are going up again if the government is serious about reducing car use. We have the most expensive public transport in Europe, with London the only capital city that expects its transport network to be self-funding. Road closure and LTNs need the full backing of the community on the basis of proper and transparent consultations.
Paul Green ● 2025d33 Comments