Study: London’s LTNs Reduce Motor Traffic On Residential Streets But Not Main Roads

A blurred young cyclist passes through the barriers that form an LTN (Low Traffic Neighbourhood), an … [+] experimental closure by Southwark Council preventing motorists from accessing the junction of Carlton Avenue and Dulwich Village. Restrictions also prevent traffic from passing through at morning and afternoon rush-hour times in the borough of Southwark, on 14th June 2021, in London, England. (photo by Richard Baker/In Pictures via Getty Images)

In Pictures via Getty Images

A large study of “low traffic neighborhoods” in London shows that these LTNs reduce motor traffic on the streets within the schemes but contrary to some claims that LTNs increase congestion on adjacent main roads, the data analysis found no knock-on increase in motor traffic on “boundary” roads.

The study found that average decreases in motor traffic on roads within LTNs is almost ten times higher than average increases in motor traffic on boundary roads, suggesting that LTNs are creating a substantial overall reduction in traffic.

Carried out by the University of Westminster’s Active Travel Academy, the study will be published in a specialist journal later in the year.

The study’s preliminary findings have been released in a report published on January 19 by climate charity Possible, which also commissioned the research.

The data analysis found that the mean average decrease in motor traffic on roads within LTNs was almost ten times higher than average increases in motor traffic on boundary roads.

Across London, the mean percentage reduction of traffic on streets within LTNs was 46.9%. This has resulted in more streets experiencing under 1,000 motor vehicles passing through them daily, implying that there may be a qualitative change in the local environment that has meant an increase in walking and cycling.

The study also analyzed the impact on boundary roads surrounding LTNs. Overall, 47% of boundary roads surrounding LTNs saw a decrease in traffic, and 53% saw an increase. Average motor traffic counts showed that traffic changed relatively little on boundary roads—with a mean average increase of just 82 motor vehicles per day, a less than 1% increase on the mean average of 11,000 motor vehicles that pass through boundary roads on a typical day.

Acknowledging this slight increase, the report authors note the importance of the substantial variations, concerning both increases and decreases in traffic on boundary roads and between individual LTN schemes.

These variations, the report points out, are not likely to be just caused by LTNs but could, instead, be caused by other contextual factors such as major local works or broader background trends.

For example, the report notes that in Newham, increases in motor traffic may be due to Olympic legacy-related development, particularly increasing motor traffic on boundary roads. This leads the report to conclude that with the installation of an LTN, there should be no expectation of an increase or decrease in motor traffic on boundary roads.

The bonnet of a car is parked almost up to a ‘planter’ of the LTN (Low Traffic Neighbourhood) on … [+] Elsie Road, initiated by Southwark Council preventing motorists from accessing East Dulwich Grove in east Dulwich, SE22, on 5th May 2022, in London, England. . (Photo by Richard Baker / In Pictures via Getty Images)

In Pictures via Getty Images

Lead author of the study, Asa Thomas, a Ph.D. researcher at the Active Travel Academy, said:

“This study finds that most streets within LTNs see reductions in most traffic, improving the experience of walking and cycling. Two-thirds of these now have vehicle flows below 1,000 vehicles a day, a rough threshold for a quiet pedestrian-friendly street, compared to only two-fifths before. What’s more, there is little indication of systematic displacement of this traffic to boundary roads.”

Report co-author Professor Rachel Aldred, director of the Active Travel Academy, added:

“The research indicates there has been overall traffic evaporation due to these schemes, as the mean average reduction in motor traffic on internal roads is around ten times higher than the mean average increase on boundary roads, adjusting for background trends. This suggests that not only do LTNs have substantial benefits inside their boundaries, but they can also contribute to wider traffic reduction goals.”

Other measures

The report emphasizes the need to consider that boundary roads are still highly likely to be polluted, unsafe, or difficult to cross or cycle on. Removing LTNs is unlikely to alleviate these issues, said a statement from Possible, making it “vital for local authorities to consider measures such as expanding low emission zones, road user charging, increasing the number of bus lanes and public transport provision, urban greenery, widening pavements, and [installing] protected cycle lanes.”

Possible is also calling on local authorities to use the report’s findings to introduce more LTNs and to challenge what the organization says is misinformation about the direct impacts on boundary roads.

They also call for further measures to address traffic on these boundary roads.

Hirra Khan Adeogun of Possible said:

“This report shows that low-traffic neighborhoods have a verifiable, positive impact on the people living on these streets. But, importantly, it shows that they have no consistent impact on boundary roads. In a climate crisis, we need our policymakers to make bold, data-led decisions; this report gives them that information. What we need now is action to drive down traffic, make our cities happier and healthier, and directly address the climate crisis.”

Sacrificial

On social media, LTN critics describe boundary roads as “sacrificial” because they claim that LTNs push motor traffic from smaller residential streets onto surrounding main roads, increasing congestion on these roads, and leading to more pollution, which impacts the residents who live on these major roads.

“These boundary roads are also where most active travel happens, and where people wait for buses, shop, and work,” said Paul Lomax, an amateur traffic data expert, who late last year spotted errors in the Department for Transport’s national statistics resulting in a correction.

“There are eight times more road traffic injuries on these sacrificial and often heavily residential roads than there were on roads now inside LTNs,” added Lomax, a vocal critic of LTNs.

Possible’s LTN study is out in pre-print.

Possible

Commenting on the pre-print of the study, Lomax said: “While the report acknowledges LTNs may increase traffic on boundary roads, this is dismissed as ‘little change.’ Given that boundary roads have ten times more traffic than the internal roads studied, this is hardly surprising—100% displacement would result in similar percentage changes. This highlights the concern that these schemes improve the least problematic roads to the detriment of the roads which most need help.”

Talking to me over Zoom, Possible’s Adeogun criticized the description of boundary roads as “sacrificial.”

“Why are they not considered sacrificial when 11,000 cars are driving down them on average every single day? Is that not already sacrificial?”

She added that introducing LTNs is just one measure that local authorities should carry out to combat climate change.

“LTNs are not the only solution for all of our congestion woes, but they are a piece of the puzzle. We also need smart road user charging, and let’s also invest in public transport and have protected cycleways.”

Lomax is open to traffic reduction measures but doesn’t believe any study has yet shown that LTNs reduce congestion overall.

“This latest report robustly analyzed fundamentally flawed data collected by councils marking their own homework. Of 96 schemes identified, only 46 are studied due to missing data, which could be a result of survivorship bias with failing schemes being pulled quickly. Councils selected the locations to be monitored, often missing key alternative routes for displaced traffic from their monitoring; it’s not only boundary roads which are impacted. And because pneumatic tube traffic counters do not count traffic below 10kmph as standard, due to accuracy issues, any increase in congestion could mask a rise in traffic flow or even show as a reduction.”

Academic

Critics often label Westminster University’s Active Travel Academy as biased, a claim disputed by Adeogun.

“The academics at the academy are transport experts, and their work is peer-reviewed in serious journals. Questioning whether experts should specialize is like saying someone who wants to defeat Coronavirus shouldn’t be researching into Coronavirus.”

The academy’s report mentions “potential disbenefits” of LTNs, including “possible journey time impacts on those with no choice but to drive, like some disabled LTN residents, whose journeys may become longer due to having to leave their neighborhood through a different route.”

On our Zoom call, Possible’s Adeogun said LTNs could also benefit some disabled people:

“There are loads of disabled people trapped because of our car-dominated landscape. Disabled people are not homogenous; they don’t have the same needs. Yes, for some disabled people, cars assist their mobility, but other disabled people cycle or benefit from wider sidewalk space for wheelchairs. We must restructure our cities to ensure they work for everyone, including disabled people.”

Adeogun added: “For people who say that main roads are sacrificial roads, I would say, yes, they are heavily polluted, so join us and help and help alleviate the problem.”