Since 1995 LEP has been operated with a bunch train scheme which allows head-on collisions of four trains of up to four bunches within a train. The proposal and its implementation are presented, and the consequences for the beam dynamics are discussed in detail. In particular the side effects due to the separation scheme itself and the parasitic beam-beam encounters are computed. The necessity of a self consistent treatment is shown and emphasis is placed on a comparison between the expectations and the observations
