  We study the properties of axial vector mesons a1 and b1 as relativistic
S-wave states which are predicted in the U~(12)-scheme, through the analyses of
their radiative and pionic decays. Specifically, partial widths of the strong
a1 (b1) -> rho(omega) pi processes, their D/S-wave amplitude ratios, and
radiative transition widths of a1(b1) -> pi gamma processes are calculated by
using a simple decay interaction model, and made a comparison with the
respective experimental values.
