[EMAIL PROTECTED] wrote:
....
> I did do a search so that I could produce a better recommendation. There
> is plenty of stuff out there suggesting that the size is too small. I
> spend a little while reading about it, but it got too scary to tinker
> with the recommendation purely in a discussion about metrication. Here
> is one example:
>
> http://www.tac-atc.ca/programs/sc/roadsafe1.pdf
Wow. I would have deducted points for some of that stuff if it were a
student's lab report. Their symbology needs some cleaning up. Their
angle notation is incorrect and they seem to put distance to the sign
over height of the letters for their ratios. But they do bring out
factors that (I think...) I think are important issues.
They seem to be saying on page 4 that a person with 20/20 vision
requires (1/12) degrees to resolve letters properly. (Though, they wrote
that as 1 over 12 degrees, effectively.) That would be only 1.5 mrad
(compare to FWHA's 2.1 mrad). But they do go on to emphasize that this
is for a person with perfect eyesight and that other factors need to be
taken into account, such as reaction and recognition times,
decision-making time, and maneuvering time. They even consider
illumination concerns, though I don't think they mentioned visibility
condition factors, such as rain. I'll give that presentation a plus for
bringing those important factors to light.
This is of some importance to me. I've done accident reconstruction
analysis and have appeared in court as an expert witness on that.
Conceivably, I might do one someday where such issues are important to
the case.
Jim
--
Metric Methods(SM) "Don't be late to metricate!"
James R. Frysinger, CAMS http://www.metricmethods.com/
10 Captiva Row e-mail: [EMAIL PROTECTED]
Charleston, SC 29407 phone/FAX: 843.225.6789
