it must be safe, the DfT had a very sudden change of heart over widening the M6 from the end of the M6 Toll to where they are going to put in the link motorway to the M56 and Manchester (which could stil be the M56 junction on the M6

) They have decided to build an M6 Toll extention roughly alongside the M6 (this will, no doubt, be scrapped in 5 years and we'll see the widening finished by 2020

).
The 85% percentile speed on the M6 Toll in good conditions is very likely to be over a ton. I've heard stories of people carriers doing 99 in lane 1 and still being overtaken.
I don't think there's been a KSI yet on the Toll, but I could be wrong. It does, however, show the speed scare-mongerers that cars don't insantly blow up at 100, unless of course they hit something.
TBH i think that average speed is rather underestimated, unless it counts time stopped at booths, or cars going slowly round the narrow and tight slip roads. Average free moving mainline speed is more like 80-85.
Simon