  In this work, a method for constructing null foliations of spacetime is
presented. This method is used to specify equivalence classes of null
generators, whose representatives can be associated lightlike co-normals that
are locally affine geodesic and thus locally orthogonal to embedded null
hypersurfaces of spacetime. The main benefit of the proposed procedure is the
fact that it is less geometrically restrictive than the traditional dual-null
approaches to general relativity, but nevertheless allows for the conclusion
that spacetimes can be foliated by suitable pairs of normalized null geodesic
vector fields. This is demonstrated by the example of different black hole
spacetimes, that is, by members of the Kerr-Newman family, according to which a
said foliation and an associated equivalence class of null generators are
explicitly constructed.
