Thanks, it makes sense. I scanned the info regarding the original accident and didn't realize that there had been so many days of warm weather prior to the guys breaking through. It does come down to awareness and common sense. Still, when you consider how many through ice accidents there seems to be each year, such awareness may be lacking.
Just found the following on the subject:
"Lakes and ponds do not freeze, or thaw, at the same rate and speed.
If something is sticking up from the ice, it will retain heat and melt a hole weakening the ice.
Travel slowly, as the speed of your vehicle can crack the ice and cause under water currents.
Single, unbroken pressure cracks are safer than smaller spider cracks. Walk slowly and carefully if you must be on the ice. The darker the ice, the more water content.
When there is moving water the water flows under the ice at a constant temperature, melting the underlying layer of ice.
Do not walk in a group as this might be too much weight.
Daredevils, show offs and speed demons bother other users, and cause a hazard, as well as underwater currents that jostle the ice.
If the ice look smooth, it may have thawed and frozen over night. It is more of a danger."
From: http://mymuskoka.blogspot.com/2009/03/a ... appen.html
Another article on possible thicknesses for various activities
http://www.lakesilkworth.org/safety/ice ... upport.htm
Going through the ice isn't a common problem in SE Florida. When I'm in the mountains, I try real hard to have subfreezing temperatures for a good portion of the trip. So, as a rule, ice integrity doesn't come into my musings. Sorry for the warmer clime perspective. Still, we have idiots racing through out of bounds guarded areas, knowing better, wonder how many people suffer lapses on the ice over time.