Among the flurry of accessibility standards the government of Ontario is developing (through the mechanisms of committees whose members you’ve never heard of) is one that governs transportation. It has the unusual requirement that, by 2025, electronic signs “achieve the appearance of solid characters.” (That isn’t exactly how it’s written, but that’s what they mean.)

Somebody, somewhere, seems to think that LED signs using a dot matrix that is sometimes or always visible are an accessibility barrier. I wonder if they’ve read the research on the subject. I have. “Synthesis on the legibility of variable message signing (VMS) for readers with vision loss” by Philip M. Garvey (2002) reviewed the literature on VMS (or its synonym, changeable message signing [CMS]).

Some dot matrices were found to be more legible than others in testing (e.g., 7×9 beat 5×7, except in one other case where 5×7 beat 6×7). But Garvey did not cite any research showing that dot-matrix signs were illegible. One of his conclusions (rephrased) is that to prove your signs are legible, you have to test them with your intended audience. People do tend to forget that.

The assumption seems to be that LCD, plasma, or some other variety of displays will be so advanced by 2025 – not coincidentally the deadline under the Accessibility for Ontarians with Disabilities Act – that they will be usable on transit vehicles. Well, do they work in –40° temperatures? Can you read the destination sign on a westbound bus near sundown in July? Will these displays really be brighter than LEDs? (Today, they aren’t. And LEDs aren’t the only dot-matrix technology in use now, either.)

The whole thing seems like the wrong solution to a nonexistent problem.

The foregoing posting appeared on Joe Clark’s personal Weblog on 2007.12.20 17:37. This presentation was designed for printing and omits components that make sense only onscreen. (If you are seeing this on a screen, then the page stylesheet was not loaded or not loaded properly.) The permanent link is:

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