Local or Rat-run?
The problem is an increased volume of HGVs using the 6 mile rural route as an East-West rat-run between the A281 and A3, and ignoring the blue “unsuitable for HGVs” signage. Surrey Highways insisted that the HGVs were only local deliveries and therefore exempt from blue advisory prohibition signs. Whilst resident data said otherwise Highways placated us (and added 18 months delay) by offering to conduct a destination survey to determine what proportion of HGVs actually were local. Resident data showed it was 82% of HGVs were through traffic.
During Covid Lockdown and in a week that was the shortest day for daylight Highways sub-contracted to a survey company that installed 6 cameras on the route. These cameras had motion sensor software and ANPR (automatic numberplate recognition). The methodology was to record the numberplate of vehicles entering in the East (camera 2) and then recording the same vehicle leaving via the West (1b) – and likewise for East bound vehicles. By calculating the time taken between captures it can be determined if HGVs took a long time to traverse the area, implying they had stopped to deliver inside the area, or if they drove non-stop through the area.
The CCTV survey data was analysed and collated into a summary report with some headline figures. The headlines delivered to the Local Committee were that 89% of HGVs were through traffic (rat-running) – almost identical to resident surveys. The overall number of vehicles traversing per day was counted as 525 (but significantly this did not tally with resident data that counted around 2700 vehicles per day.) The destination survey was failing to count 4 out of 5 vehicles that passed the cameras. Once the raw data was analysed by residents it was clear there were significant technology failings and flawed methodology in analysing the data. The cameras needed to capture a specific vehicle number plate on both entry and exit cameras for it to be counted. The technology was unable to do that consistently. The analysis methodology inexplicably was set to reject any vehicle that took longer than 7 minutes to get from Loxhill to Hydestile. Residents know that the time taken to do that journey can be anything from 5 minutes to 18 minutes, depending on hold ups.
Salt Lane normally shows equal daily totals East and Westbound, but with a tidal flow – mainly Eastbound in the morning and Westbound in the evening (particularly commercial/construction traffic). Because Surrey’s cameras didn’t count during dusk their data missed the evening peak hour Westbound traffic so their daily totals erroneously show Eastbound movements to be nearly double that of Westbound.
These flaws, and others resulted in the undercount of just 525vpd – showing a very poor 20% success rate in capturing vehicles passing the cameras. If you extrapolate that figure to include the missed vehicles it totals 2620 ( close to residents’ own survey totals of 2700). For Highways not to recognise that disparity in their new data is incompetence. To report their flawed conclusions to a committee is negligence.
The Local Committee wasted £5000 on this unreliable Destination Survey – a survey that was conducted to fob off the residents and delay action on addressing the real and increasing problem of rogue HGVs.
For those of you with an eye for statistics, the review of the flawed survey is here:
Surrey Highway’s original summary findings are here. Take note that there are no logs of any vehicles taking longer than 7 minutes. Note it declares a success rate of 83% of motion capturing vehicles, but fails to state the success rate of the ANPR. Note there are no HGV counts after 3.30pm.