I was only trying to have a little FUN with the "route".... and as usual learn along the way - as many people "here" have driven various routes that would have taken them along these freeways...
I've always figured 60 mph AVERAGE when towing... the trucks take longer to fuel - and you can't bob and weave in traffic - and you have to stop for some roadside "relief" -- after eating McDonalds at the truck stops... I even make my own coffee along the way - and keep a thermos full at all times. I'm a coffee snob - since I don't drink - and take my whole beans - grinder - and maker with me wherever I go...
I have played with the "route" --- I 40 vs I 10 -- I 40 is shorter in milage even thought it doesn't look it on the map... and at 60 mph 'average' -- it's almost 2 hours shorter. But what the routes don't tell you - which is why I said 'lets talk about it' - is hills etc which can really toss a wrench in your 60 mph average if you don't have the capacity to haul some serious butt...
I drove I 10 once - through Midland and Odessa I had to wear a large handkerchief over my face to keep the "west Texas dust" out of my nose. I followed a truck because I couldn't see where I was going. When I woke up the next day in Shreveport, Louisiana -- it had rained - and the streets ran with RED west Texas dirt...
It sand blasted the front of my 2002.... and I had to get it painted when I finished the trip.