For the KEK B factory, the necessary horizontal separations between beams at the peripheral collision points are given by means of the rigid Gaussian model. For the present design parameters, (1) in the head‐on collision scheme, bunches can be filled in every three buckets and 2 mm separation is enough at the point 1.8 meter distant from the interaction point, (2) all buckets can be filled if the crossing has an angle of 3 mrad (half angle). The limitation comes from a reduction of the luminosity and the excitation of the closed orbit at the arc and (1+2). The combination of (1) and (2) with crossing angle of 2 mrad and 0.6 T separation magnets (all buckets being filled) provides enough luminosity and enough space for the final focus system.