Yes, I agree. The flow of traffic for most commuters, like myself, seem to around 75 mph.
"The speed limit is commonly set at or below the 85th percentile operating speed (being the speed which no more than 15% of traffic is exceeding)[41][42][43] and in the US is typically set 8 to 12 mph (13 to 19 km/h) below that speed." http://en.wikipedia.org/wiki/Speed_limit
"The speed limit is commonly set at or below the 85th percentile operating speed (being the speed which no more than 15% of traffic is exceeding)[41][42][43] and in the US is typically set 8 to 12 mph (13 to 19 km/h) below that speed." http://en.wikipedia.org/wiki/Speed_limit