A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Gary LaPook
Date: 2017 Dec 19, 15:22 -0800
Everyone knows that I rail against illogically high levels of precision in navigation computations. Of course it infects other areas in our world I watched the coverage of the train derailment yesterdy and the talking heads were all aghast that the train was going 81.1 mph in a 79 mph zone. Oh horrors of horrors. This is another illustration that most people don't know how to deal with numbers. One-tenth of a mile per hour, what possible difference could that make? Even two mph over the limit couldn't make a difference since they have much larger safety margins built in when they set a speed limit. One mile per hour is 1.47 feet per second so one-tenth of a mile per hour is 0.147 feet per second, 1 and 3/4 inches per second! These people (like most) have no conception of scale or what the numbers they are talking about really mean. They found the speed of the train on this website.
Anyway, it turns out that there was a lower speed limit of 30 mph in the curve before the bridge.