Depends on the interstate. My average, over ground speed, for this trip was between 75-85 mph. I was, basically doing about 10 mph over the limit, which put me in the slightly faster than the slow-lane drivers.

In Canada I was doing about the same, but it wasn't 10mph over the limit, it was more like 20. It's not the actual speed I was commenting on, but the difference between the posted, and the traveled.

There were places on 401 where the baseline traffic was doing 120kph, in a posted 80 zone, and the people I was following were still doing 130.