Curious Road Markings

A number of red surface rectangles have appeared with this one the most northerly on the southbound carriageway. It now has SLOW in both lanes on these rectangles. The ones to the south have yet to be marked. They occur before a slip exit and before a slip entry. They are not easily visible, there are no other road edge markings, there is no need for any warning, particularly in lane 2, as traffic entering the slips only slow in the slip. There may be a case for entry slips but usually the presence of a joining vehicle is sufficient. I have not seen any indication that anyone slows down. Please reconsider.