The previous Conservative government had initially been supportive of Low Traffic Neighbourhoods (LTNs), consistent with its positive attitude to promoting active travel. But before the general election of July 2024, it swerved, recognising the unpopularity of some schemes, seen by some as anti-motorist. In my own neighbourhood, the local authority engaged residents on a proposed LTN scheme last summer, which generated a good deal of opposition from those that thought they would be adversely affected, and a petition of more than 3000 signatures. The environmental scrutiny committee of the local authority held a meeting this week at which deputations could express a view. I had previously prepared a note on the topic, and had the opportunity to make a short oral presentation. The substance of my note follows, omitting specific references to locations in the neighbourhood.
The previous government commissioned a review of the evidence of the impact of LTN schemes, which reported in March 2024. A total of 99 schemes were identified, of which 82% remained in place and 18% had been removed. The main conclusions derived from all the evidence collected were that LTN’s are effective in reducing traffic on internal roads, although outcomes for boundary roads were mixed; air quality on internal roads has improved, but that on boundary roads varied; and impact on walking and cycling has been mixed.
Transport for London has summarised experience of LTNs in London, concluding that the evidence to date consistently shows that they are having a positive impact on the lives of people living and working in London, although the impacts take time to develop.
There have been academic studies, notably Thomas and Aldred’s review of 46 London LTNs for which monitoring data was available, finding substantial falls in traffic within schemes, but on boundary roads little change in the overall average traffic but substantial variation across schemes.
In general terms, it would be desirable to reduce through traffic within the nighbourhood, the magnitude of which seems to have been increasing in recent years, likely due in part to the wide use by drivers of satnav that indicates the fastest routes, often on smaller roads that are best suited to walking and cycling.
The evidence presented in support of the proposed LTN includes historic traffic count data for many of the roads. But no information is available on the origins, destinations and purposes of trips, which means that traffic modelling of likely outcomes of the scheme is not possible. Gathering information on trip origins, destinations and purposes requires considerable effort and expense, employing household and roadside surveys, GPS and mobile phone data, and in general would only be attempted for proposed major road schemes, not for proposed LTNs. So one can only speculate about likely changes to traffic flows in a specific case. But because implementing the LTN does not involve major and irreversible road works, a trial-and-error approach is justified, encouraged by the findings of the 80% success rate noted above and by the withdrawal of 20% which failed to meet expectations.
Nevertheless, some questions about likely changed traffic flows may be posed. For instance, judging by the difference in flows at the morning peak between school term time and holidays, there is a fair amount of ‘school run’ traffic. This seems likely to be mainly the consequence of residents dropping off children at schools outside the neighbourhood, as well as non-residents driving children to the secondary schools within the neighbourhood. But without knowing which schools are the destinations, it is hard to estimate to what extent such trips would persist with the implementation of the LTN (the alternative being more children making their own way), but taking more time and covering greater distances, so generating more traffic to offset the reduction in through traffic having no business in the neighbourhood.
In the absence of traffic modelling of likely flows with the LTN in place, we can only pose questions about the key outcomes:
- The net overall traffic reduction: the extent to which the reduction in through traffic is offset by increased distances travelled to addresses in the neighbourhood by residents, delivery vehicles, taxis etc, as well as increased distances travelled by residents out of the LTN.
- The extent of diversion to boundary roads.
- The extent of ‘disappearance’ of traffic.
‘Disappearance’ refers to the way in which traffic reduces in response to some impediment to flow. Time is always a constraint on travel. Impediments such as congestion or, in the present case, the need to travel greater distances, prompt some drivers to make alternative choices where feasible: an alternative route where delays are less, an alternative mode of travel, an alternative time of departure, an alternative destination (for instance for shopping), or not to travel at all (such as ordering goods online). There is good evidence for the reality of traffic disappearing, although the extent depends on the nature of the location. The availability of good public transport is helpful. One possible source of traffic disappearance would be if parents bring forward the point in time when they cease to take their children to school by car, letting them travel independently by public transport or on foot.
Entry of vehicles into the LTN is intended to be controlled by a mix of fixed barriers and camera-enforced controls, both forms open to use by cyclists and pedestrians. Given the inevitable uncertainties about travel volumes, both for individual roads, internal and boundary, and in aggregate, two varient approaches are worth considering. First, to exempt residents from penalty charges for passing camera-enforced traffic filters. This would allow residents to take the more direct route, reducing traffic in the neighbourhood, while blocking through traffic. Second, the camera-enforced traffic filters might operate only at peak times, as for Healthy School Streets, preventing the bulk of through traffic.
It would be usual to implement the LTN for a trial period before a decision on firm plans. It is common with such schemes to initially implement by means of an Experimental Traffic Order, which is limited to a period of 18 months while the effects are monitored and assessed, after which decisions are made whether or not to continue with the changes on a permanent basis. A commitment by the local authority to a reliable means to assess local opinion would be desirable, based on data from monitored traffic flows before and after scheme implementation. It is worth recalling that the local Neighbourhood Plan was adopted by the local authority in 2020 following a local referendum.
The engagement phase for this particular scheme has concluded. I expect the next phase will be a formal consultation on a modified plan that responds to the concerns expressed, as far as feasible. I also expected that the outcome of that will be a trial implementation, which is likely to show that some of the concerns will not be borne out in practice. A key question will be whether there is a significant increase in traffic on the boundary roads. If not, I would expected the LTN to be made permanent.