The following article has been written by Michael De Haan, a local resident:
Do people enjoy being deceived by Enfield Council ? It turns out that the traffic surveys done by Enfield for their post LTN data applied a filter so that it did not count any vehicles moving at less than 10km per hour. The individual road reports show not a single vehicle on any road doing less than this speed. Given the congestion introduced by the LTNs this is highly unlikely. This means that the figure quoted for the percentage increase in traffic on the boundary roads should be close to double that reported in the Fox Lane Final Report.
These falsely low figures were also the ones used to generate the pollution models. I have been in contact with the manufacturers of the equipment used (MetroCount) and they say the equipment, which relies on two rubber tubes strung across the road, is recommended to only be used in FREE FLOWING traffic. When you introduce congestion, and vehicles stop with their wheels between or bridging the tubes, or they do not travel over the tubes fast enough, the vehicles are simply not counted. Preparing a report with a 10km filter from this raw data increases the number of vehicles not counted. In severe congestion, where cars only shuffle forwards a couple of car lengths at a time you will not count 25% of the cars (that’s one in every four). Even in milder congestion where cars move forwards 10 car lengths at a time you will miss 5% of vehicles (one in every 20). On 6th July 2021 Transport Survey Systems, the company employed by Enfield Council, did what are known as “Turning Surveys” at four junctions on four of the Fox Lane LTN boundary roads. These surveys video the traffic for 12hrs and the number of vehicles manually counted. This was during a week when the same company were also surveying the same roads with the Automatic Traffic Count (ATC) tubes. By comparing the data you can show the ATC tubes didn’t count nearly 3000 vehicles that were manually counted over the 12hr period. This represents 5.4% of the total traffic over this 12hr period that was simply NOT COUNTED. As there was an hourly breakdown of the figures you can show the number of missed vehicles increases in direct proportion to the level of congestion.
Nearly all surveying of LTNs over London use this method. If there is little or no congestion at the count points, pre LTN, the number of vehicles counted will be fairly accurate. If the LTN creates congestion at the count points then the post LTN survey will simply not count a proportion of the vehicles. Maybe this is what is meant by traffic evaporation?
Comment: It is well known that measuring traffic congestion based on traffic counts is a defective method. The only safe way to measure traffic congestion is to time a trip when there is no significant delays (e.g. in the middle of the night) and compare it to the travel time in busier periods. To allow for odd incidents or delays, the average of several trips needs to be taken. This was the method used by TfL when initially reporting on the effect of the Congestion Charge.
That showed that there was no benefit in the Congestion Charge in terms of reduced congestion and TfL subsequently ceased publishing similar reports for obvious reasons. See this web page for more analysis of the Congestion Charge and its impact: https://www.freedomfordrivers.org/congestion
Note that a campaign group against the LTNs in Enfield are going to the High Court on the 25th October as part of a legal challenge. See https://www.gofundme.com/f/stop-the-ltn039s-fox-lane-amp-enfield and here: https://stopfoxlaneltn.org/
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