I'm always intrigued by a press release which goes against the evidence of my own eyes. And so it was with yesterday's TfL press release on Green Person Authority.
New TfL data shows success of innovative ‘pedestrian priority’ traffic signals
This is a follow-up to a trial announced in a press release in September 2020, but delayed until May 2021 because the pandemic muted traffic levels.
Transport for London has published new data that shows how innovative Green Person Authority traffic signals could be used to make walking in the capital safer and easier.
(Back in 2020 this was a Green Man Authority project but someone's had second thoughts and now it's Green Person Authority instead. This may be a wise move in an era of gender equality but it was only last year that TfL proudly launched 23 sets of traffic lights with Green Women to try to improve diversity, and I don't think you can have it both ways. Sorry, I digress...)
In May 2021, TfL installed the new technology at 18 crossings across London. These priority signals show a continuous green signal to pedestrians until a vehicle is detected approaching the crossing. The signal then changes to red for pedestrians, allowing the vehicle to cross the junction before returning to a green signal for pedestrians.
I was excited because one of these 18 trial sites was very near me, on Devons Road outside the DLR station, so I'd be able to see what all the fuss was about.
In effect, this switches the need to ‘demand’ a crossing from pedestrians to vehicles, giving priority to pedestrians at all times other than when a vehicle is detected approaching the crossing.
As I reported last May I was surprised because the Devons Road signals weren't behaving the way they should have done. Under Green Man Authority the traffic lights are supposed to stay red until there are no pedestrians and some traffic. But at Devons Road the lights only ever stayed red for the normal length of time, then switched back to red again when they spotted no traffic was coming.
I've crossed this crossing dozens of times during the trial, and observed it dozens more, and never once did the green man show for longer than normal. It was always six seconds and then the countdown started and traffic was allowed to pass again, even when there wasn't any.
As part of the switch on process, each site was monitored in person by one of TfL’s Network Managers to ensure the technology was operating correctly.
It may be that TfL’s Network Manager signed off on the correct behaviour at Devons Road and I am systematically mistaken, but I cannot reconcile what should be happening with what I've actually seen.
New data from the trial suggests that the pedestrian priority signals reduced journey times for people walking and made it easier and safer for them to cross.
It's no surprise that if you tweak crossing signals to prioritise pedestrians, pedestrians will find it easier and safer to cross. The numbers are much more interesting (or were when I managed to find the trial report TfL had failed to link to in the press release).
The average location involved in the trial displayed a green pedestrian signal for an extra 56 minutes a day.
It's not actually 56 minutes extra green time per day, it's 56 minutes extra during the 12 hour period 7am-7pm. This works out at almost six minutes extra per hour, which isn't much, and supports the conclusion that buses and other vehicles weren't adversely affected.
But this was not what I observed at Devons Road. During one particular five minute period only one pedestrian turned up wanting to cross the road, but during that time the lights changed from green to red and back again an astonishing nine times. That's approximately one minute (out of five) of extra green... enough to hit the "56 minutes extra green time" target in a single hour, not across a day.
By reducing the waiting time for a green signal, the total time saved by all pedestrians at the average crossing in the trial was 1.3 hours a day.
As a collective total, 1.3 hours doesn't sound much. If I assume the Devons Road crossing sees 1000 pedestrians a day, it's the equivalent of saving 5 seconds each - nice to have but not life changing. The trial report suggests the key factor is the number of vehicles passing, and that sites with over 7000 vehicles were likely to generate a measly 10-35 minutes additional pedestrian green time.
Compliance with traffic signals by people walking increased by 13 per cent, reducing the risk of a collision with a vehicle, while compliance by people driving stayed the same.
This is hardly rocket science either. If pedestrian signals are green for longer then the percentage of pedestrians crossing on green should increase. What's encouraging is that signals were only green for an extra 8% of the time, so the 13% increase in compliance is a decent improvement.
At one location, Bishopsgate with St Helen Street, a significant increase in pedal cycle red light violations per traffic signal cycle was observed. This increase is above the trend experienced at other sites and is likely to be a result of large cycle numbers, which is around 600-1000 more pedal cycles per period than other sites.
It seems bikes and GPA don't mix, perhaps because cyclists are impatient but more likely because approaching cyclists fail to trigger the lights. Whatever, there are so many bikes on Bishopsgate they turned the trial off.
The trial report provides three important conclusions (none of which are picked up in the press release).
Future deployment...
• ...should focus on locations with fewer than 7000 vehicles in a 12-hour period (particularly crossings on one-way streets or part of Low Traffic Neighbourhoods)
• ...can only be implemented at locations with fewer than 150 pedal cycles per hour over all time periods
• ...cannot be implemented on any site with an 85th percentile speed of above 35mph
I'd add that Green Person Authority needs to be implemented properly, so not the incorrect switching I've seen on Devons Road (and whose data has presumably contributed to these conclusions).
Following the results of the trial, TfL is assessing how the technology could be further improved and used at other locations across London in the future.
So you might see Green Person Authority in action at your local standalone pedestrian crossing.
Funding for further sites across the capital would be dependent on agreeing a long-term funding deal with the Government.
