Highlights
- Article systematically reviews London Low Traffic Neighbourhood monitoring data.
- Meta-analysis of pre-post data from 587 count locations from 46 schemes.
- Substantial falls in motor traffic within LTN schemes, especially in Inner London.
- By contrast, little average change in motor traffic on LTN boundary roads.
- LTNs can form part of wider traffic reduction schemes alongside other measures.
Abstract
This paper meta-analyses traffic data extracted from monitoring reports for 46 Low Traffic Neighbourhood schemes in 11 London boroughs introduced between May 2020 and May 2021. Schemes are controversial with still limited academic evidence on impacts. The analysis covers internal and boundary roads, looking at actual changes in motor traffic, and at what changes might have been expected based on background trends in London’s three ‘functional zones’ (Central, Inner, and Outer). All metrics show substantial relative declines in motor traffic on internal roads. For instance, a mean ‘pre-LTN’ traffic volume of 1,780 dropped to 930 ‘post-LTN’, against a small projected decline to 1,745 if background trends were followed. By contrast, the schemes are only marginally associated with change in traffic volume on boundary roads. While there are inevitable data limitations associated with the use of routine monitoring data, this research provides some support for the position that LTNs can form an effective part of wider strategies to reduce motor traffic and its associated disbenefits. Monitoring data should be publicly shared regionally and nationally to aid analysis.
1. Introduction
Since the start of the Covid-19 pandemic, Low Traffic Neighbourhoods have been introduced in London, and to a lesser extent, other parts of England. LTNs are schemes that seek to reduce motor traffic in primarily residential areas, using traffic management measures such as ‘modal filters’ to block general motor traffic while permitting walking and cycling.1 They seek, like many other traffic management measures, to combine ‘carrot’ and ‘stick’ by encouraging use of sustainable transport while discouraging car use. The design principle of LTNs is not new: in the Netherlands, this approach to urban planning is called ‘unbundling’, referring to the goal of separating much motor traffic from people walking and cycling (Schepers et al., 2013). However, research is still emerging on the retrospective introduction of these measures, with stronger evidence for increased walking and cycling than for decreases in car use (Aldred et al., 2021a, Aldred et al., 2021b).
London offers an opportunity to study the impacts of such schemes at scale. Within six months of the pandemic starting, newly introduced LTNs in London covered 4% of the population (Aldred et al., 2021a, Aldred et al., 2021b). By March 2022, a hundred schemes had been introduced, although a minority had been removed. This scale is noteworthy given the city’s complex governance. In London, most transport planning is done by 33 individual districts, which control more than 90% of the roads. Transport for London (TfL) manages ‘strategic roads’ (many but not all ‘A’ roads) and oversees much funding to districts, including that provided during Covid-19 for emergency schemes such as LTNs. Generally, districts decide where such schemes should be placed, in negotiation with TfL, which produces strategic analyses that boroughs may refer to in guiding scheme placement.
Planning approaches differ across London districts. One-third chose not to implement any LTN schemes and others vary both in the number of schemes and in the extent to which those schemes are located in more or less deprived or diverse areas (Aldred et al., 2021a, Aldred et al., 2021b). Processes by which districts decide whether and where to implement LTNs can be opaque and differ depending on, for instance, technical capacity as well as political leadership (Furlong et al., 2023). This has led to differences in the equity of their distribution (Aldred et al., 2021a, Aldred et al., 2021b) and may also potentially mean their impacts vary by district. Approaches to monitoring and evaluation also vary substantially, with a few London districts producing lengthy reports covering a range of potential LTN outcomes including metrics such as injury or crime numbers, most using only traffic counts to measure changes in vehicle numbers at specific locations, and other districts not reporting on any monitoring or evaluation metrics. Given this and the devolved nature of London transport planning, there is no city-level monitoring and evaluation of these schemes.
Within the UK (and beyond it, e.g. Nello-Deakin, 2022 on Barcelona’s Superblocks), much debate around the impacts of these types of schemes has focused on possible disbenefits for residents and road users on roads to which motor traffic may be displaced from inside an LTN (usually called in the UK ‘LTN boundary roads’; Hickman, 2021). Previous studies examining motor traffic capacity reduction suggest such schemes typically induce a mixture of motor traffic redistribution and traffic evaporation, for instance, through mode shift (Cairns et al., 2002). However, Cairns et al. (2002) found that the balance varied substantially from almost all redistribution to almost all evaporation. The nature of this balance will make a large difference to the overall impacts of a particular group of schemes. In response, this study systematically reviews and meta-analyses routine monitoring and evaluation data from 46 London LTN schemes to draw conclusions about changes in motor traffic within the schemes and on their boundary roads.