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Whilst I may not always agree with Tom on interpretation of data, his data on the traffic counts is accurate.There are however 2 or 3 issues which from the data it is impossible to fully quantify/assess.1. We know that prior to LTN some 10k vehicles were cutting through Grove Park, but we do not know how many were Chiswick residents simply taking the obvious route home.  Long term it might be good to have an exemption for registered Chiswick residents to allow them to take the short cut - easy to check with cameras reading the number plates.  That might ease traffic issues at the roundabout without significantly adversely affect GP residents or it might result in too much traffic using the cut through2. We do not know how many people coming over the bridge end up using the flyover and how many use the roundabout, although I suspect the data is out there somewhere.  This is crucial to know because the phasing of lights at roundabout needs to take that into account.3. Finally, we need rigorous data on how many vehicles are queuing throughout the day to know whether we have a capacity issues throughout the day or merely at certain times.Of course it is possible that traffic counts are down because of people working from home - although that should result in the same reduction seen across the borough applying to the bridges whereas as Tom shows the reduction at the bridge is greater.  There could be a number of explanations as to why the reduction is greater, I suspect part of it will be fewer people shopping in Richmond due to how difficult the journey has become.  No doubt we will soon have figures for 2023 which may show the trend of reduction continuing, or not

Justin Stephenson ● 289d

Jeremy, your clarified statement is completely meaningless in terms of understanding the effect of traffic! If any bridge is closed, then comparing to a second bridge the proportion of traffic on that second bridge will increase. It tells you nothing about whether that in itself causes an issue. My comparison in absolute terms and to the change in the borough average tells you whether any road can be expected to cause issues, either currently or in the future, due solely to the closure of the bridge. On that basis the closure of Hammersmith Bridge is not causing issues in terms of traffic crossing Chiswick Bridge as traffic is lower by both measures. My other point was to quantify that around 70% of traffic from the A316 entering or leaving Grove Park was non-residential.  There is no reason that Grove Park should suffer the effects from that, given there is a route designed to take such through traffic via Hogarth roundabout. Of course that means that through traffic will now continue up to Hogarth roundabout, but as less traffic is crossing Chiswick bridge in the first case, this most certainly is not leading to unprecedented levels. In fact traffic twenty years ago was measured regularly above the current levels, and the vehicles would have been more polluting as well.Given the latest figures for crossing Chiswick Bridge in 2022 are now down to 30k and assuming the 3k of that accessing Grove Park is the same as 2021, 27k vehicles a day were travelling past Edensor Road, well below the average number for previous years. Overall, with the lowest number, and cleanest, vehicles crossing Chiswick Bridge since 2000, Chiswick overall will be suffering considerably lower levels of pollution from traffic coming in and leaving on the A316.https://roadtraffic.dft.gov.uk/manualcountpoints/6902

Tom Pike ● 289d

Tom, I'm not sure what point you are trying to make with this data but I did choose my words carefully. It is incontravertible that if you have fewer bridges to cross there will be a higher proportion of crossings over the remaining bridges.You also seem to think that people are arguing that the Grove Park LTN hasn't succeeded in its main aim of succeeding in reducing through traffic. While there is a flaw in your argument in that just because a vehicle reaches Edensor Road it can't be assumed that it isn't heading for Grove Park - if it doesn't have access, it would need to carry on to Hogarth Roundabout and double back - there is no questioning that traffic is effectively being discouraged using Hartington Road and Staveley Road by the ANPR cameras.You don't say whether these numbers are for both directions or just northbound but either way several thousand extra vehicles a day need to continue on to Hogarth Roundabout. My point is that if you combine this with a possible reversion to the mean of traffic levels generally in London, the number of vehicles arriving at the the A316 junction with the A4 northbound will reach their highest ever levels.As you know relatively small increases in traffic levels can have a disproportionate impact on congestion because a junction only needs to go marginally over capacity before queues develop. There appear to be increasingly consitent reports of queueing traffic back to Edensor Road and beyond. Would it not be sensible to start monitoring the impact of this on local air quality near schools and housing?

Jeremy Parkinson ● 289d

"...the Hammersmith Bridge closure will mean more proportionately more vehicles are crossing over Chiswick Bridge."We have traffic counts for Chiswick Bridge from 2017 to 2022:2017: 35k2018: 35k2019: 38k2020: 33k2021: 32k2022: 30k2022 counts are down 13% from 2017 and 2018, before the closure. Over the same period, traffic was down 9% in Richmond and 4% in Hounslow. So not only is traffic crossing the bridge down absolutely, but also as a proportion of the traffic in both the boroughs either side of the bridge.The traffic counts can also indicate the effects of the Grove Park LTN. In 2017 there were 25k vehicles counted on the A316 at Edensor Road compared to the 35k crossing the bridge, which means 10k were accessing Grove Park. The other year we have manual counts at both locations, 2002, 42k were crossing the bridge and 32k were counted at Edensor Road, again meaning 10k were accessing Grove Park.In 2021 the counts at Edensor Road had increased to 29k compared to 32k crossing the bridge, meaning only 3k were accessing Grove Park, now only as residents with permits. Comparing 2017, 2002 and 2021, that implies 70% of the traffic entering Grove Park from the A316 was non-residential before the LTN was established.Paul is quite correct to say that such data is not going persuade anyone with a fixed view, but they are a minority: it is interesting to note that attitudes shift once people recognise that traffic changes are in their own self interest, hence why opposition to the LTN within Grove Park is falling away, just as it has with the ULEZ expansion. Sadiq Khan deserves some credit for both sticking to his policy as the right choice, despite heavy pressure to delay it, and having the political acumen to realise that he would benefit electorally, beyond the short term.

Tom Pike ● 290d

Interesting to see that research confirms what common sense suggests about the notion of traffic evaporation. It would be nice if traffic did magically disappear but the reality is most of it gets displaced.Everyone posting here would accept that increasing road capacity will induce extra demand and increasing it will reduce it. We are all aware of cases in which cities have been completely blighted by catering solely to motor vehicles. However, there is no such thing as 'The Law of Traffic Induction', it is just one factor that needs to be considered in making complex decisions about traffic management. Others include existing capacity and elasticity of demand.London's problem going forward is not induced demand but a return to the peaks seen in 2019 due to a return to normal working practices and increasing economic and population growth. Since then capacity has been reduced in this section of west London due to the Grove Park LTN and the closure of Hammersmith Bridge. Up until now this has not had an easily measurable impact on congestion but, based on what people are reporting here and elsewhere, congestion on the A316 seems to becoming more and more acute.In a city like London with good existing public transport links, the scope for people to switch to alternative means of travel is limited, therefore the number of journeys no longer taking place due to the congestion may not have enough of an impact to reduce the congestion. The elasticity of demand on the A316, where many people are coming into London because the public transport alternative is unviable or two expensive, is likely to be particularly low.It is too early to reach firm conclusions about what is happening on the A316 but queues down past Edensor Road do seem to be becoming more common. As I've said before, it would be best to start collecting evidence early about what impact this was having in air quality in the area particularly next to Cavendish School and housing on Burlington Lane as exceedences of WHO limits provide the main risk to the health of people in the area.

Jeremy Parkinson ● 293d