I have been walking and sailing on the Ice on Winni and many other lakes in New England since 1969. Early ice is "Black Ice". That is what we are seeing now (Web Cams). (Ice boating..Remember Don Kent..? He was an Ice boater AND a weatherman out of Boston.)
Black Ice is the best. You can look down through the ice..It's CLEAR..At the cracks you can see how thick the ice is. You have to use
"Judgment"..as to how thick it is.
I have walked and sailed on 2.5 inches of
Black Ice. The ambient temperature is also important. Best Below freezing while you are out there.. No Bob Houses, snow machines...etc... just pedestrians.....
And ICE Boats OK. The weight load (Pounds per square foot on the ice is light.)
One time: I was ice boating on 2.5 inches of good ice ..
in the rain ..temp maybe 40..on Norton Reservoir in Mass.
Went for a Swim. 
Once the lake (Winni) "Catches"...If the temperature at night is below 21 degrees..it can build an
Inch a night.
Once snow....melting ...and refreezing gets involved...all bets are off. ICE Experience counts.
NB
PS: I have no experience on how much ICE is needed to support your SUV or a Motor Home...I have seen those on the ice..