Well I always assumed that a carraige way was a dual carriage way even if it had no central reservation, if it was more than one lane. A bit off thread slightly but thhat means the section between the M56 and M6 south isn't dual carriageway. It's got a limit on it now with proper signs, but back when it was national, That means I and nearly everyone else was speeding. I cant find any reference to footpaths
http://www.highwaycode.gov.uk/09.htm#103