Slide to unlock


was crossing a street in Heemstede the other day, and I noticed a braille sign above a pedestrian button. It showed an embossed number “3”, a divider, and, I assume, that number in braille. I wasn’t familiar with this sign and I could not figure out what this number was telling me and how it was related to the pedestrian button.

'3' is the magic number

After a bit of research I found out that these were actually instructions to use the “Rateltikker”. The “Rateltikker” is a sound produced by the traffic light pole and indicates whether the light is red (slow ticking sound) or green (fast ticking sound). The sound is activated by pressing the button, but it turns out that always hearing this sound can be annoying (if you live right next to it), or more importantly confusing in case there are multiple ticking traffic lights close to each other and you don’t know where to listen to. Another way of putting it is that the sound-feature is very important, but it is only needed in specific occasions. Therefor a “user interface obstacle” is built in, to prevent unintentional clicks of the button.

It reminded me of the long-press of [command-Q] when closing the Chrome browser (Hold Q to quit).

Hold Command-Q to quit
Hold Command-Q to quit

The instruction (the number 3) indicates the number of seconds that someone has to press the button, in order to activate the rateltikker. It is the key to activate the Rateltikker-sound. It sounds like smart idea, but to me, this sounds very much like an expert-user feature. Of course I'm not the target audience and not familiar in this field, but it does make me wonder how this is tested, implemented, communicated.

Fun fact that I learned during my research is that there are multiple variations of these crosswalk sound. Some beep, some tick, but there also used to be a variation with bird sounds called the “cuckoo-chirp signal”. The “chirp” sound was used for a east-west crossing and the other one plays a “cuckoo) for a north-south crossings. Over time other birds started mimicking these sounds thus creating a dangerous situation; the sounds have now been replacedsounds have now been replaced…