  Universal velocity addition formulas analogous to the well-known formula in
special relativity are found for four geometrically defined relative velocities
in a large class of Robertson-Walker spacetimes. Explicit examples are given.
The special relativity result is recovered as a special case, and it is shown
that the spectroscopic relative velocity, in contrast to three other geometric
relative velocities, follows the same addition law as in special relativity for
comoving observers in Robertson-Walker cosmologies.
