A crossing gate mechanism includes a gate mechanism enclosure, a gate arm shaft, and a quick-replacement moon gear assembly. The gate mechanism enclosure defines an interior space. The gate arm shaft extends into the gate mechanism enclosure and is rotatable relative thereto. The quick-replacement moon gear assembly is coupled to the gate arm shaft for rotation therewith and is positioned within the interior space. The quick-replacement moon gear assembly includes a gear hub fixed to the gate arm shaft for rotational movement therewith, and a quick-replacement moon gear releasably coupled to the gear hub. The quick-replacement moon gear is removeable from the interior space while the gear hub remains fixed to the gate arm shaft.