Originally Posted by
unterhausen
Pennsylvania has a couple of interstates where the speed limit is 55, seemingly for the same reason. It doesn't keep people from going 80, but it does increase the variability in speeds, which makes things more dangerous. Pennsylvania puts orange diamonds on interstate speed limit signs where they know the limit is too low and is not commonly observed. I have no idea why they don't just increase the limit instead.
Maybe it's a loophole to keep from losing highway money from the feds.