[gnicholas]

Seems OK at first glance, but if you're in a 65 then the trucks (in the right lane) will want to go 65+. Going 55 in the right lane means they all need to pass you, which causes a domino effect onto the other lanes of traffic. If you're on a 4-lane highway (2 in each direction), going 55 means that trucks that pass you will have to go in the fast lane.

If there aren't a lot of trucks around, then going 55 in the right lane has less of an impact on other drivers. But if there are many trucks (which there usually are, IME), then going 10 MPH under the limit will cause a lot of headaches for all the other drivers around you.

[MBCook]

And that’s 65. I’ve been in places where the speed limit is 70 but people usually go 75-80.

That’s 20-25mph faster than you. At that point you’re practically impeding traffic, and having a big truck pass you is terrifying.

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

[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.