Do LTNs Cut Accidents?

A study on Low Traffic Neighbourhoods (LTNs) by Anna Goodman et al, which has been widely reported by the Guardian and the Mayor of London, suggests that road casualties have fallen dramatically in London after LTNs were introduced. The fall is as much as 50% overall with large falls in pedestrian casualties.

One might say that if roads are closed and traffic reduced (the main objective of LTNs by their advocates although the Covid epidemic was used as the excuse to do so) then accidents are bound to fall. On the logic that the end justifies the means then to reduce the high road casualty toll, all roads should be closed. But that would not be very practical.

But if you look at the study, you will realise that it is hardly a scientifically accurate study of the impact of LTNs.

The key measure to look at when considering road accidents is the Killed and Seriously Injured (KSIs) where the data in this study seems to be very small, as minor injuries can suffer from under reporting. That is particularly so in the pandemic as people would be reluctant to visit police stations to report accidents.

In addition it seems a lot of the reduction is to pedestrians who were probably much reduced, particularly on busy shopping streets where most casualties take place, because of the pandemic. Few people were going shopping other than via the internet during the pandemic (many shops were closed), and the elderly and young, who are most prone to road accidents were particularly avoiding going out (schools were closed for example). The data has not been adjusted to take account of these factors.

The other issue is that road safety professionals consider that a three-year before and three-year after comparison is best used when considering the impact of road changes. This is because if road layouts are changed there tends to be a significant but only short-term impact on road user behaviour.

This is very selective data over a short period of time and not likely to reflect longer term trends. It is a great pity that Sadiq Khan has promoted this report without thinking. There are many good reasons why LTNs are opposed by the majority of people and LTNs are not a good way to reduce road accidents. All such simplistic solutions will fail because the reasons for accidents are complex and scientific studies need to have proper “controls” in place before conclusions are drawn. In this study, why were pedestrian casualties much reduced while other types were not and what features of the LTNs may have reduced accidents? There are several ways to implement LTNs but the report tells us nothing about those issues.

Reference: https://findingspress.org/article/25633-impacts-of-2020-low-traffic-neighbourhoods-in-london-on-road-traffic-injuries 

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