this post was submitted on 03 Sep 2025
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Only in cameras.
One could paint stripes in tunnels lit by cheap LED or sodium vapor lamps (that flicker at 100/120 Hz) that appear stationary at the speed limit. I wonder how drivers would react.
I've seen this in Vancouver, Canada, between Burrard and Granville station. unfortunately they're used to display advertisements. The trains don't have drivers and are controlled remotely from a central location.
That's very much not what I meant. These stripes would be passive (just paint) and you couldn't really customize them because sodium or unsmoothed LED lights' flicker has a 50% or greater duty cycle, blurring any design beyond recognition.
What you're referring to are persistance-of-vision ad displays around passing trains in tunnels. These require active electronics and even accurately measuring the train's speeds.
The system in Vancouver does use electronics to create the flashing, but I'm pretty sure it just synchronises to to average speed of the train because the illusion is quite inconsistent. It will almost always scroll forwards or backwards from the rider's perspective. It probably does help that the sky train speed is controlled by a computer, leading to more consistent results.
Yup, Prague's system I know is the same as Vancouver's, possibly by the same company, but I've never seen it sync badly. The system I'm proposing are simple painted stripes, the flashing is the nature of existing lighting.
I wonder how physically resilient the LED bars in Prague are, since the windows can open enough for someone to extend a stick to damage them.
They did this in San Francisco several years ago as well! It was a neat proof of concept but it didn’t stick around super long.
Especially not if the trains have windows that open slightly like Prague's, allowing someone to just extend a cane and destroy the whole installation.
Badly I would assume