  We discuss a way to obtain the doubly special relativity kinematical rules
(the deformed energy-momentum relation and the nonlinear Lorentz
transformations of momenta) starting from a singular Lagrangian action of a
particle with linearly realized SO(1,4) symmetry group. The deformed
energy-momentum relation appears in a special gauge of the model. The nonlinear
transformations of momenta arise from the requirement of covariance of the
chosen gauge.
