Maybe it`s something to do with all the rules,regs and red tape all over the place,is everyone supposed to know everything about everything now? maybe it`s the sign on the rear of many HGV`s that states"limited to 56" or some other mis-information everyone should know about? Why they put these signs on "could" be part of the reason,not everyone gets everything absolutley right 100% of the time,sorry about that.It's a weird misconception this..... Speed limit for HGV on a motorway is 60, and has been for decades. The 55 idea was to save fuel, and it works. Quite how the majority have come to believe the limit is 55/56 - I have no idea!