Never pull into single file to let someone past, not even on a single track road. On a standard road, if they can’t get past without taking to the opposite carriageway, they can’t get past. Even in single file, the motorist still has to give you 3 feet (1.5 meters ) clearance ( They often don’t ) so a single line of riders in ‘primary’ will still need the motorist to take to the opposite carriageway, but if the cyclists are in a single line, it will be longer, and increase the motorists’s T.E.D. So many people don’t get this fact, it’s amazing. On a single track road, find a passing place, and stop out of the way.