Whereas in the UK 56 mph is the governed maximum, there seems to be a noticeable difference in speeds of trucks (as seen on the 'Big Rig' video
http://www.bigrigtravels.com ).
A very rough calculation (by me) suggested that 'Big Rig' achieved 54mph average (including minor roads, some congestion in city traffic and a 20 minute break) and many trucks are travelling much faster. It's difficult to determine how fast 'Big Rig' travels but it seems 'moderate'. Obviously unrestricted 400HP trucks are capable of significant speeds (particularly when unladen), but are there speed limits on US highways (and are these enforced on toll-roads by time taken between toll booths?)?
Does anyone know what is the 'average'?