I'll say that my locale is oddball in that we have a lot of cyclists (5% for work commutes but almost double that if you include school commutes as we have a large university) and drivers don't typically speed. In fact it's common for drivers to be under the speed limit. An arterial near my house sees a lot of 25 in a 35. It's not that the traffic is bad, just that drivers don't race around.

Most of my riding is on MUPs, 25mph residential, 55mph farm roads, and 30mph arterials. My city has a lot of commuter-designed MUPs and a grid of bicycle routes (replete with bridges) that are low speed and low traffic. There's just not a need to use 45mph arterials except for short distance store access.

95% of the roads I drive on are 45 or 50mph posted multilane (2-3 in each direction)
I prefer this as I get my own lane if I want.

Commuting to work half of my ride is on a four lane, 55-70 mph highway-much of it with no berm. The good news is it isn't heavily travelled, meaning I usually get my own lane (although I ride AFRAP). The rest of my commute is a mixture of industrial and residential streets. When riding for pleasure, 35-40 mph sparsely driven country roads-much more enjoyable.

I live in the country. I ride state routes, back country, and dirt roads. Near work I am on non-neighborhood country residential roads. No matter what the road or the limit is, traffic can be 45-65 mph. That is if you would call it traffic. If I encounter 5 cars in well over an hour, I consider that encountering a lot of traffic.