alt Hacker News> US speed limits are highly variables, they’re generally 55 in the north-east but on the western half they’re 65 to 70, and 75 in TX.
I fear even that is misleading. Yes, the speed limits on undivided highways are often 55 in the north-east (or even 50 in a couple), but the speed limits on divided highways are all higher, ranging from 65-75 mph. See the two maps on the top right: https://en.wikipedia.org/wiki/Speed_limits_in_the_United_Sta.... I suspect that the majority of truck miles are on divided highways.
A number of the major freeways immediately around Boston are 55. Almost nobody actually drives slower than +10 mph. If you go 55 in the slow lane you'll get passed by other people in the slow lane!
I've seen truck speed limits of 55 pretty much everywhere I've been except Texas, though.