Low-traffic neighborhoods significantly reduce the amount of motor vehicles within their boundaries without appearing to push traffic onto the roads around their edges, the most comprehensive study of such schemes in the UK to date has concluded.
The research, which was based on traffic count data before and after the installation of 46 so-called LTNs in London, found a reduction in car traffic within the zones of 32.7%, measured as a median, and a drop of 46.9%. calculated as the mean.
Of the 413 roads within the LTN with pre- and post-traffic counts, the percentage averaging fewer than 1,000 motor vehicles per day, seen as a good shorthand for a street receptive to more cycling and walking, rose from 41% to 66%.
This could mean a “qualitative change in the local environment” on at least some streets due to LTN, the researchers said.
LTNs use either physical filters, such as bollards and planters, or traffic cameras to prevent motor vehicles from using some smaller residential streets as through routes while bicyclist and pedestrian traffic is unaffected.
Opponents of the schemes, which have proved controversial in places, with several removed, argue that they do not reduce the overall volume of car traffic, but simply move it to other roads.
Graph for LTN traffic data
While the authors behind the study from the University of Westminster’s Active Travel Academy (ATA) noted that they only had usable data for just under half of the 96 LTNs installed in London between March 2020 and May 2021, but said that there is considerable general evidence of so-called traffic evaporation.
Data from the 174 border road census points showed what the authors said was a more mixed picture, but with no apparent evidence that such roads necessarily saw more traffic after the LTN was installed.
Of those observed, 47% saw a decrease in car traffic, and 53% saw an increase. When measured as an average, the overall average for border roads rose by 2.1%, but fell by 1.6% when calculated as a median.
When the totals were adjusted using Transport for London data for wider changes in traffic to account for factors such as the Covid-19 pandemic and different seasons, border roads had an overall average increase of 0.7% in motor traffic , or an average of 82 vehicles per day.
Within this, the researchers found what they called “significant variation in both directions” of border roads. They concluded that this was mainly due to non-LTN factors, such as other works, and said more research could be done to reduce traffic on border routes.
The study also noted other caveats, including that the majority of the census was carried out in inner London rather than the more distant suburbs, and that the extent and quality of traffic data provided by councils varied, with some not at all have carried out monitoring.
The researchers also pointed to the need for further study of other effects of LTN, including how best to mitigate its impact on people who especially need to drive on local trips, such as some people with disabilities.
The research was funded by TfL and the climate charity Possible and carried out by the ATA.
Asa Thomas, a PhD researcher at the academy and lead author of the study, said the findings point to a significant decline in vehicle traffic within the LTN, along with “little indication of a systematic shift of that traffic to border roads”.
Prof Rachel Aldred, director of the ATA and co-author of the study, said: “The study shows that there is an overall ‘traffic evaporation’ as a result of these schemes, with the average reduction in car traffic on inland roads being around 10 times a high-than-average mean increase in borderline paths adjusted for background trends.
“This suggests that not only do LTNs have significant benefits within their boundaries, but they can also contribute to broader traffic reduction goals.”
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