TomTom estimated driving times

[happy_face]

I was wondering if any one knew what speed the sat nav bases its calculations on?

If it's going on national speed limit would it then not shorten the journey time if you drove on German motorways as there is no speed limit?

What I'm trying to find out is that I'm due to drive in Europe and my TomTom route planner tells me it's going to be 6 hrs from one place in Holland to a particular place in Germany. But if it's calculating on 70mph then surely it would take us less time

thanks