Driving at 56mph versus 75mph is 75% so a 6 hour drive becomes 8 hours.
If you think that two hours of extra driving in a particular day is not any considerable time, then I have a bridge in Brooklyn to sell you.
As I have stated many times I will be driving on highways throughout Europe, where you don't regularly get slowed down by traffic.
I made the trip in reverse when I moved from Portugal to England 10 years ago so I know the roads and I know the traffic conditions.
As I have also stated on this thread, it is more dangerous to drive slowly on a highway than drive at the same speed as almost everybody else, especially given that a lot of these roads are only two lanes in each direction.
I would have to drive with large trucks that give off petrol or diesel fumes rather than driving with cars that give off less fumes.
Also these particular drives on the highways are incredibly boring and I want them to take as little time as possible.
Do I need to explain more or can you just accept that my original question was posed based on my particular situation and I do not need to change my question or do something different because somebody else here cannot understand that my life is different to theirs?