Evaporating traffic? The impact of low-traffic neighbourhoods on main roads

Orford Road, Walthamstow - once traffic-clogged, now a social space

Low-traffic neighbourhoods can be life-changing for the residents who live in them. Since the neighbourhood improvements in Walthamstow Village in 2015, people are walking and cycling more, children play out, air pollution has improved and life expectancy increased.

More information on what low-traffic neighbourhoods are and how they work is available here.

But bold traffic plans such as this are often introduced amid concern and opposition. This series of blogs explores these questions and presents research that helps fill missing gaps and tackles any misunderstandings.

Here we examine concerns that low-traffic neighbourhoods may divert traffic onto main roads leading to increased congestion and air pollution.

Traffic evaporation 

Experience reveals that predictions of traffic problems caused by low-traffic neighbourhoods almost always fail to materialise, and that significant reductions in overall traffic levels across an area can happen as a result of people making a wide range of behavioural responses to the new traffic configurations.  

The most comprehensive study of the phenomenon of disappearing or “evaporating” traffic was carried out by Sally Cairns, Carmen Hass-Klau, and Phil Goodwin in 1998 and followed up in 2002. See below and here.

This brought together experience from 70 case studies of roadspace reallocation from general traffic, across 11 countries, with opinions from 200 transport professionals. It shows that traffic does not behave like water moving through pipes, finding an easier path as another narrows. Instead it is a force of human choice, driven by people making all sorts of different decisions when driving conditions change. The respondents in the Cairns study, for example, changed their mode of travel, chose alternative destinations, or the frequency of their journey, consolidated trips, took up car sharing or didn’t make the journey at all.

In half of the case studies, over 11% of the vehicles which were previously using the road or the area where roadspace for traffic was reduced, could not be found in the surrounding area afterwards.

More people walk in low-traffic neighbourhoods 

What’s really encouraging, is that one of the most significant behaviour changes following implementation of low-traffic neighbourhoods has been a shift to more walking and cycling.

Just one year after the implementation of  schemes in Outer London, including Waltham Forest, residents were walking 32 minutes and cycling on average 9 minutes more per week. This ongoing London School of Hygiene & Tropical Medicine and University of Westminster study is available below and here.

As Rachel Aldred, reader at University of Westminster and one of the study’s authors says, “new infrastructure often takes some time to have an effect on active travel, but in this case we are seeing positive results after only one year”.

This demonstrates that if councils improve the conditions for walking and cycling (and make driving just a little more inconvenient), people take the bait very quickly. And as time goes on, as active travel becomes embedded in lifestyles, more will follow leading to long-term change over an entire area.

Shrewd city planning

Low-traffic neighbourhoods are not, therefore, about rewarding one group of people while punishing another: they are part and parcel of shrewd city planning, making long-term decisions about how people travel.

And the potential for change is massive: currently around 1.6 million, or 22%, of all car trips made by London residents every day are under 2km and could therefore be walked (2.7 million more could be cycled). See below and here.

Any measures for converting these car journeys to active modes should be of paramount importance for London boroughs – not just to reduce traffic volumes but to improve the health of communities through activity and lower air pollution.

A 2018 study by King’s College London (more below and here) linked the boost in active travel in Waltham Forest’s low-traffic neighbourhood with increased life expectancy as a result of improved air quality, increased activity and shift to active travel on the school run.

This research also found that more than 51,000 households in Waltham Forest are no longer living in areas with dangerously high levels of air pollution compared to a decade ago.

Impact on main roads

So what about the main roads? Even with traffic evaporation, main roads will shoulder some extra traffic. But evidence suggests the impact of this isn’t as big as some fear.  Waltham Forest’s research shows that bus journey times (on main roads) have not significantly increased following introduction of LTNs.  That research is available here, chapter four.

King’s College London research, based on modelling work where traffic volume is used as one of the inputs to determine air quality, suggests that there has not been a decrease in air quality on main roads following introduction of LTNs. That report is here, page 8-9.  

Main roads were also designed to take the majority of traffic, so can absorb increases in traffic better than their residential counterparts. These streets have wider carriageways, with buildings set further back. They also have better crossing facilities and safer junctions.

A small increase in traffic on a main road is also less noticeable than the transformation brought about by a dramatic reduction on a residential street: of a child riding a bike to school, of walking to the local shops, or hearing birdsong again. And given the majority of people in London live on residential streets, these sorts of improvements could be life-changing for millions.

For an illustration of how non-local traffic can degrade the environment and safety of residential roads, watch this video Stoke Newington, London. https://twitter.com/mum_on_bike/status/1138444799139356683

Counts on main roads in Waltham Forest also showed that traffic was more spread out across the day following introduction of the low-traffic neighbourhoods. In fact, maximum peak hour flows were lower on the main roads. In other words, the traffic Armageddon that some expected never arrived.

All that said, any increase in traffic is hard to accept if you live on a main road or send a child to school there. As a result, main roads also demand urgent attention.

Action for main roads

One solution, being adopted in many cities across Europe and in Britain (for example in Glasgow), is to reconfigure main roads as urban “boulevards”. London also has the benefit of the Healthy Streets Approach to help deliver this sort of change. Urban boulevards could feature, for example:

• wider, better pavements;
• lane reductions;
• removal of parking;
• bus lanes;
• cycle tracks;
• speed restrictions;
• more crossings;
• more seating, trees, and planters; and
• closed side streets and banned right turns to increase capacity and reduce congestion and air pollution.

Wider road traffic reduction policies are also necessary and increasingly possible, including:

• workplace parking levies;
• parking restrictions; and
• a 24/7, London-wide, distance-based road user charging scheme, now on the cards for the longer term. Read Centre for London’s report on Next generation road user charging here.

These wider policies, plus redesigns of main roads and low-traffic residential schemes should all be addressed in unison, even if they are delivered over different timescales.

Doing nothing is no longer an option

The alternative — of proponents of different approaches falling into opposing camps – will only result in inaction, or watered-down schemes and lengthy delays. And there isn’t time for this.

London’s population is set to grow from around 8.6 million today to 10 million in 10 or so years. There simply isn’t space for all these people to fit in cars on roads. Climate change, air pollution and the health impacts of inactivity are also at crisis point, requiring immediate and drastic action. As the research listed here demonstrates, low-traffic neighbourhoods are one of the easiest, quickest and cheapest ways to take on this challenge.