Also.. if an a.c is lined up for say 27L. But the spacing is getting tight, for what ever reason. The ATCO may offer the pilot to take 27R visually, to save a go around etc.
Can't remember the the correct term for this.
There are airports with 3 runways in parallel, and are used for 3 approaches in parallel too. ** Left ** Central and ** right. Maintained with visual separation.