[editor-surveyor]

Safety is the main reason why 85 MPH is appropriate.

Traffic that is slugging along behind a rolling roadblock is never safe.

[matt04]

I don’t know if it’s true, but I read somewhere that many highways are designed to have traffic drive at speeds higher the the posted 55 or 65.

[hinckley buzzard]

Drove across Montana on I-90 last summer. I'd say 85 was about what cops call "the flow of traffic."

Historical note: When the Pennsylvania Turnpike opened, the first divided highway in America, it had NO speed limit. Signs at the entrance gates merely said, "please drive carefully."