One simple tweak to traffic lights could transform cities for pedestrians

In low-traffic areas planners are turning the signal system on its head — will it work?

Walking around Los Angeles carrying a bag of rice the rough weight of a three-year-old child last month, it became clear how difficult it can be for pedestrians in a city, particularly those who move more slowly — kids, caregivers, the impaired or the elderly.

The exercise — part of the the Urban 95 Expert Assembly conference — was a stark reminder of how cities in their current form disadvantage slower movers. When the green man turns red and you still have a lane of traffic left to cross, the stress mounts.

It can mean people are discouraged from walking at all. Research suggests that poor experiences of crossing the road might be enough to discourage disabled people from even going out in the first place.

But London’s government is hoping a small, almost imperceptible tweak could make a big difference for the city’s pedestrians. Over the next six months the city will trial a new scheme to reprogram pedestrian crossings to continuously show green. The aim is to get more Londoners out onto the streets and walking around the city.

So will simply changing traffic lights be enough to make life better for a city’s pedestrians?

Walking with difficulty

“There’s a view that some locations in London are dominated by traffic — perceptions [are] that traffic signals can be an impedance, or a reason why people choose not to walk,” said Helen Cansick, head of network performance at Transport for London(TfL), whose team is responsible for running the city’s 6,100 traffic signals.

Her team wanted to help the city’s march towards a goal of 80% of trips made on foot, by cycle or using public transport by 2041. “We wanted to try some different techniques,” Cansick continued, “that really quite rapidly turn the way that we operate the traffic signals on their head.”

Though standard signal systems, in theory, give both drivers and pedestrians the same amount of time to cross an intersection, in reality pedestrians are subtly disadvantaged.

At pedestrian crossings, signals usually flash 10 seconds before the signals change, warning people off from even beginning a crossing. In contrast, on-road traffic lights show drivers just 2 seconds of amber light before changing, giving them more time to drive through without hindrance.

And most signals are timed to the assumption that the pedestrian will be able to cover 1.2m a second, a figure set in the 1950s, and something only very few elderly people are able to manage.

Signal change

Cansick’s team took inspiration from London’s buses. The city has two bus-only streets, where buses begin and end their routes.

One bus starts a journey only once every seven minutes or so, so it makes little sense for pedestrian crossings over these streets to constantly change. Instead, sensors will detect when a bus needs to leave, and change the signal accordingly. The rest of the time the signal is set as green for pedestrians.

Cansick and her team looked for areas in the city where traffic was low and pedestrian traffic high at certain points throughout the day, and selected 10 as potential places to trial the scheme, named “green man authority”. At these crossings, the lights will now constantly display the green man signal until sensors detect a vehicle approaching.

Political will

Signal timings are established through a constant system of analysis and review. Nevertheless, both Cansick and Dr Rachel Lee, Policy and Research Coordinator at Living Streets, point out that, historically, signal systems have been engineered to move motor vehicles efficiently, but not pedestrians.

The Mayor’s walking action plan gives TfL the mandate to alter this. Though, according to Cansick, there “will be winners and losers” at every set of signals, green man authority will help rebalance the trial areas in favour of pedestrians. By making walking a central part of their transport plans, politicians can give planners and engineers the room to trial new ideas, fail if necessary and try again.

Moving forward

The pilot of green man authority will run until around March 2019, after which an evaluation will take place to assess its effect on the whole network. Using a whole host of TFL transit data, the team will work out whether the changes succeed in increasing pedestrian activity.

Before then, there are challenges to overcome. While TfL’s sensors can easily detect approaching cars and change the signal to allow them through, they are less effective at identifying cyclists. They also need to make the system work for visually impaired pedestrians, who use specially-designed vibrating cones attached to each crossing to know when to cross. These would wear out too quickly if they vibrate constantly. Cansick and team are working on adaptations — extra sensors, and a button activated cone, to solve it.

Ultimately, Lee argues that what pedestrians need to feel at home in cities is more space and safety to walk. “If you want to make London a world class city,” she said, “you need to have more people walking and cycling.” The aim of the green man authority pilot is to win back some of that space for walking, by helping make it safer and more comfortable — the next year will reveal whether it works. — Anoush Darabi

(Picture credit: Flickr/jimbohne)


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