People tend to drive at what they think is a reasonable speed. The sign put out there on the highway doesn't control it nearly as much as the perceived condition of the road - hills, curves, volume of traffic out there.

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Interstates and parkways ... we recommended going to 70, and some of the four-lane non-interstate, non-parkway roads we recommended going to 60 miles per hour from 55. Many of the rural interstates are now six lanes and not four lanes like they were at that time, which, in my opinion, makes them even safer.

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