We show that the relative Farrell-Jones assembly map from the family of
finite subgroups to the family of virtually cyclic subgroups for algebraic
K-theory is split injective in the setting where the coefficients are additive
categories with group action. This generalizes a result of Bartels for rings as
coefficients. We give an explicit description of the relative term. This
enables us to show that it vanishes rationally if we take coefficients in a
regular ring. Moreover, it is, considered as a Z[Z/2]-module by the involution
coming from taking dual modules, an extended module and in particular all its
Tate cohomology groups vanish, provided that the infinite virtually cyclic
subgroups of type I of G are orientable. The latter condition is for instance
satisfied for torsionfree hyperbolic groups.Comment: 30 pages, to appear in Annals of K-theor