Tuesday 10th May 12:08 pm
Traffic button pushes beautiful design
Tuesday 9th February 2016 5:38 pm
Next time you’re at the lights, stop to appreciate the humble pedestrian button. The design is so beautiful that even Oscar Wilde would approve, says Dr Karl.
In 1884, the playwright and world-class wit, Oscar Wilde, wrote, in The Value of Art in Modern Life:
“I have found that all ugly things are made by those who strive to make something beautiful, and that all beautiful things are made by those who strive to make something useful.”
What would Oscar Wilde think of the PB/5 — the standard push button that Australian pedestrians press when wanting to cross the road at a traffic light? And anyhow, what is there to know about a push button?
The answer to that second question came to me when one of my techo friends invited me to sit in on a two-hour lecture he was giving to audio engineering students. It was called “A Brief Introduction to Switches and Buttons”.
There’s a lot to know about switches and buttons.
If you look around your house, you’ll quickly see that most of your switches take your device from ‘on’ to ‘off’, and back again. But some of your switches are ‘momentary’ — they operate only while you still hold the button.
But switches get way more complicated once you get into computers and their associated hardware. I have one crazy switch (a KVM switch, or keyboard, video, mouse switch) that does three different operations, depending on how long you hold it down for — 0-3 seconds, 3-15 seconds and longer than 15 seconds). (By the way, I was having some troubles with this KVM switch, and I eventually found this essential information on page 45 of a 180-page manual!)
In some Australian cities, in the central business district, the traffic light push buttons don’t work at certain times — for example, 7 am to 7 pm, Monday to Wednesday, and 7 am to 9 pm, Thursday to Saturday.
The rationale is that between these busy hours, the road traffic is relatively constant, and also, the pedestrian crossings are in continuous use. So the lights do their own thing.
However, the traffic light push buttons do work outside these hours, including all day Sunday.
Now if you’re designing a switch for pedestrians to use when crossing the road, you need something robust, elegant and intuitively easy to use by everybody — and that includes pedestrians who happen to be blind, deaf or otherwise distracted.
The Australian PB/5 (patented way back in the 1980s) has all this under control. Its official name on the patent is “audio-tactile pedestrian push button signalling system”. It’s been exported to the USA, Ireland, New Zealand and Singapore.
You’ve seen the PB/5 — a 25-centimetre-high box with safe rounded edges bolted onto a traffic pole at a pedestrian crossing.
The circular upper half has a distinctive large white arrow on a blue background. It has a smaller raised arrow inside it, so that visually impaired people can feel it. The bottom half has a generously sized stainless steel concave circular button.
You’ve also heard the PB/5 — slow ‘chirps’, followed by a single ‘kapow!’, and the urgent ‘tick-tock-tick-tock’ sound. These sounds are all part of the elegant and intuitive design.
First, the slow chirps (the ‘don’t walk’ signal) alert you once every two seconds that this is the time to wait. It also tells where to wait. The patent describes the ‘chirps’ as the ‘locator sound’ — so that visually impaired people can easily find the RP/5. The frequency has been specifically chosen to be identifiable in city traffic noise.
Second, the single ‘ka-pow’ noise (called the ‘change tone’) alerts you that something has indeed changed.
Third, the rapid tick-tock-tick-tock sound (the ‘walk signal’, repeated eight times per second) tells you to get moving.
In the upper half, the artwork of the blue arrow on the white background is anodised onto a circular metal plate. This metal plate is coupled to a ‘transducer’. As part of the elegant design, this single ‘transducer’ does three jobs.
First, the transducer acts a loudspeaker to make the three different sounds.
Second, it acts as a microphone that listens to the ambient city noise. This then controls an internal amplifier to make the loudspeaker louder or softer, so that you can hear it above the city noise, but not too loud that it might become irritating.
Third, the transducer can vibrate the upper metal plate in different modes that correspond to the different sounds. This means that deaf people can touch the metal plate, and know whether to wait, or walk.
As switches and push buttons go, the PB/5 is way ahead of the pack.
I feel sure that Oscar Wilde would the love the usefulness, and beauty, of the PB/5 audio-tactile pedestrian push button signalling system.
This blog first appeared on Dr Karl's Great Moments in Science
© 2016 Karl S. Kruszelnicki Pty Ltd