[Tomte]

Don't you have construction sites or slower cars?

I'm regularly driving 150 kilometers on the fabled Autobahn, with no speed limit for the most part (and some 120 km/h speed limit sections), and the difference between "I feel great, let's drive 180" and "Let's take it slow and drive 100 or 110" is surprisingly small, because that top speed is only attainable for short stretches of time.

[dsfyu404ed]

Obviously traffic varies by city, road and time of day but on the nominally 55-mph section of I95 around Boston traffic flows between 65 and 90ish if it's not precipitating with the exception being peak commuting hours when the choke points cause enough of a disruption to make most of the system flow well below that speed. Even if you knock 10mph off those speeds because older cars aren't quite as quiet and smooth at any given speed it still results in traffic speeds well above 55.

All the 55mph limit on that particular road does in my mind is give law enforcement a pretext to make fishing stops.

I can't recall a time I ever saw traffic go ~55 on a limited access road without the presence of inclement weather or severe traffic congestion. When you consider the kind of traffic conditions that are the norm in rural ares I don't think a national 55mph speed limit makes sense at all.

Edit: I'm curious to know how a comment that is simply stating my observations and opinions can be considered so wrong.