  We present a causal trajectory interpretation for the massive vector field,
based on the flows of rest energy and a conserved density defined using the
time-like eigenvectors and eigenvalues of the stress-energy-momentum tensor.
This work extends our previous work which used a similar procedure for the
scalar field. The massive, spin-one, complex vector field is discussed in
detail and solutions are classified using the Pauli-Lubanski spin vector. The
flows of energy-momentum are illustrated in a simple example of standing waves
in a plane.
