Thanks, Shamrock - I'm familiar with the 'conceptual' width and we normally 'offset' 1 or 2nm - it was the actual width I was after, and Mr R's post is the closest I have got. This was prompted some time back when the spacing halved and it is often difficult to execute a 180 in 15nm. The suggestion (from the '15nm' parallel rule) would be that the tracks would be probably 20nm 'wide', I guess, giving a 5nm margin? Mr R's MPNS 12.6 nm limit makes it quite close!