[jcranmer]

> Just because you can legally drive 55 or maybe even less doesn’t make it safe.

Generally, you actually can't legally drive that much slower than prevailing speed.

[gnicholas]

I remember seeing minimum speed limit signs in Iowa. I was told this was to keep tractors off the highways.

Where these signs aren’t present, I think you’d have to be going more than 10 under the maximum limit to get a ticket.