Riding along the A17 towards Kings Lyn and came across the section in the photo. Basically a single carriageway then splits with grass in the middle to separate traffic turning off. It is a national speed limit area so 60mph but there are 60mph signs before and NSL signs after. I am presuming it is classed as a dual carriageway even though it isn't single lane due to to the grass separation. Signs are there to say 60mph instead of 70mph normally associated with dual carriageways?
https://www.dropbox.com/s/7kuyq0e7b9sg8d1/Photo%2029-07-2019%2C%2020%2020%2018.png?dl=0
https://www.dropbox.com/s/7kuyq0e7b9sg8d1/Photo%2029-07-2019%2C%2020%2020%2018.png?dl=0