  A novel numerical scheme to solve coupled systems of conservation laws is
introduced. The scheme is derived based on a relaxation approach and does not
require information on the Lax curves of the coupled systems, which simplifies
the computation of suitable coupling data. The coupling condition for the
underlying relaxation system plays a crucial role as it determines the behavior
of the scheme in the zero relaxation limit. The role of this condition is
discussed, a consistency concept with respect to the original problem is
introduced, well-posedness is analyzed and explicit, nodal Riemann solvers are
provided. Based on a case study considering the p-system of gas dynamics a
strategy for the design of the relaxation coupling condition within the new
scheme is provided.
