Yes, because that's how the Highway code says you should drive - 15 seconds is a plenty big enough gap to pull over into! Obviously if you need to pull out again after 3-5 seconds then that's different. It's because people don't pull over to the left and continue to drive in the centre lane that causes the situation where there are no gaps to pull out into. It effectively reduces a 3 lane motorway to a 2 lane motorway! Yes, but it also states that the national speed limit is 70mph! If I'm travelling at 70mph in the middle lane overtaking two lorries then theoretically it shouldn't make a difference if I pull back in or not!