Hi,
I'm building some LED safety blinkies for my bike helmet. The project itself is trivial from a technical point of view, but I wanted to make sure that the lights wouldn't be likely to trigger a seizure in someone with photosensitive epilepsy. I found a resource at: http://www.epilepsyfoundation.org/aboutepilepsy/seizures/photosensitivity/guidelines.cfm
which seems to indicate that I'll be fine if I keep the flashes under two per second, especially since the lights will not be terribly bright and will not occupy a large part of anyone's field of view.
Are there any other guidelines that I should keep in mind?
Epileptics will be sensitive to their triggers, and are likely to have developed their own defense -- such as looking away from things that are likely to bother them. If you're thinking "but drivers can't just look away, they need to watch the road!" Anyone that does not have their seizures under control through medication should not be driving to begin with. At least in the places I've lived, you have to meet a certain criteria (no seizures in six months, for e.g.) before you're legally allowed to drive. (I've known a couple people who did anyway, but they didn't immediately react to a couple blinks, and had a similar defensive mechanism to non-epileptics who were approaching oncoming traffic with headlights on at night -- look to the other side of the road.)
Lots of things blink in this world, and while it's kind of you to consider that, if you're on a roadway somewhere there will be other things flashing anyway. For example, turn signals and flashing traffic lights. Don't be any more offensive than those, and you're probably doing enough.
Thanks for the input, that helps a lot. I didn't realize that people who are affected can detect possible triggers and avoid them, though I guess I should have. I don't really know enough about it, I suppose.
From the PoV of a web developer, if there's a simple thing I can do to help e.g. people with screenreaders, I'll do it - add alt attributes to img tags, provide navigation skip links, add ARIA roles, etc. If there's trivial thing I can do with this project to prevent epileptics from having to turn away e.g. fire the LEDs at 2Hz vs. 5Hz, I don't see any reason not to do that as well. If it makes me just as visible but makes me less likely to inconvenience someone else, why not? I just don't know all of the triggers that could induce a reaction.
Thumbs-up.. It's always nice to know someone's keeping those things in mind. (Funny - the web dev aspect came to mind immediately while reading your original post.)
SirNickity:
If you're thinking "but drivers can't just look away, they need to watch the road!" Anyone that does not have their seizures under control through medication should not be driving to begin with.
I do recall an article in the "Heckler" column in the Sydney Morning Herald a few years back, regarding people with inobvious disabilities being criticised for parking in "disability" parking spots, and citing epilepsy as one such inability. I considered the opinion piece particularly perverse at the time since of course, less than fully controlled epileptics indeed can not be driving, and these parking spots are not "disability" in the more general sense as such anyway as actually quite specifically "mobility impaired".
SirNickity:
At least in the places I've lived, you have to meet a certain criteria (no seizures in six months, for e.g.) before you're legally allowed to drive.
Paul__B:
I do recall an article in the "Heckler" column in the Sydney Morning Herald a few years back, regarding people with inobvious disabilities being criticised for parking in "disability" parking spots, and citing epilepsy as one such inability. I considered the opinion piece particularly perverse at the time since of course, less than fully controlled epileptics indeed can not be driving, and these parking spots are not "disability" in the more general sense as such anyway as actually quite specifically "mobility impaired".
That stuff bugs the crap out of me. I know someone that uses their disability tag to take advantage of those spots. Yes, the person has a disability. But not in the way that justifies the act. IMO. People can be so selfish...
hogmartin:
Hi,
I'm building some LED safety blinkies for my bike helmet. The project itself is trivial from a technical point of view, but I wanted to make sure that the lights wouldn't be likely to trigger a seizure in someone with photosensitive epilepsy. I found a resource at: Epilepsy Foundation #1 trusted site for epilepsy and seizure news
which seems to indicate that I'll be fine if I keep the flashes under two per second, especially since the lights will not be terribly bright and will not occupy a large part of anyone's field of view.
Are there any other guidelines that I should keep in mind?
Slow blinking risks being invisible to a quick glance, fast blinking near 7 to 10Hz is bad
for epilepsy, so why blink? Steady light is much easier to localise in a busy environment
anyway.
MarkT:
Slow blinking risks being invisible to a quick glance, fast blinking near 7 to 10Hz is bad
for epilepsy, so why blink? Steady light is much easier to localise in a busy environment
anyway.
What SirNickity said, basically. At twilight, against a backdrop of stores, signs, and other cars, I feel that a steady light from my little LEDs are too easily mistaken for windshield glare or a reflection in a window. I'm not counting on it being my only illumination - I have reflective gear and there are streetlights and headlights, and I rarely ride in complete darkness. In that situation, it seems that a steady, periodic blink indicates an actual attention-demanding indicator and not a spurious reflection. I have no actual science to back this up, but it does seem to be the case on the occasions when I do drive: a blink catches my eye and a steady light doesn't.
I prefer to see bicycle blinkies that stay continuously lit, dimly, in between bright strobes. The strobe is attention-getting; the constant burn allows one to assess the bearing and distance much more accurately than a strobe alone.