Relative hyperbolicity, classifying spaces, and lower algebraic K-theory

For $Gamma$ a relatively hyperbolic group, we construct a model for the universal space among $Gamma$-spaces with isotropy on the family VC of virtually cyclic subgroups of $Gamma$. We provide a recipe for identifying the maximal infinite virtually cyclic subgroups of Coxeter groups which are lattices in $O^+(n,1)= iso(mathbb H^n)$. We use the information we obtain to explicitly compute the lower algebraic K-theory of the Coxeter group $gt$ (a non-uniform lattice in $O^+(3,1)$). Part of this computation involves calculating certain Waldhausen Nil-groups for $mathbb Z[D_2]$, $mathbb Z[D_3]$.