To enhance computational efficiency of ring-polymer molecular dynamics (RPMD), reduced-dimensional models are proposed for X + YCZ(3) -> XY + CZ(3). In these models, bond parameters of CZ(3) are fixed keeping the C-3v symmetry. These models are denoted by r-RPMD, t-RPMD, p-RPMD, i-RPMD, and irc-RPMD. Extensive RPMD calculations in both full-and reduced-dimensional fashions are performed for H + CH4. The computational efficiency of the reduced-dimensional calculation is found to be enhanced by a factor of roughly 3.5, which is close to 4 (factor for 12D -> 3D). Good agreements between irc-RPMD and previous results are found. (C) 2018 Elsevier B. V. All rights reserved.