It's just hyperbole. The English use miles per hour there's literally no reason for it. Also having driven the one road in Texas with speed limits that high,

It's just hyperbole. The English use miles per hour there's literally no reason for it. Also having driven the one road in Texas with speed limits that high, semi-trucks do not go 85mph. I was not passed once, nor had a semi-truck gain on me. It's simply not fuel efficient for trucks to go that fast (nor cars honestly). ~75mph maybe... to make up time but faster than that and fuel efficiency is surely so bad they lose time having to refuel. Towns are also so sparse and far between the danger of running out of gas is real with moderately poor planning.