  The quantum kicked rotor (QKR) model is a prototypical system in the research
of quantum chaos. In a spin-$1/2$ QKR, tuning the effective Planck parameter
realizes a series of transitions between dynamical localization phases, which
closely resembles the integer quantum Hall (IQH) effect and the plateau
transitions. In this work, we devise and apply the finite-size scaling analysis
to the transitions in the spin-$1/2$ QKR model. We obtain an estimate of the
critical exponent at the transition point, $\nu=2.62(9)$, which is consistent
with the IQH plateau transition universality class. We also give a precise
estimate of the universal diffusion rate at the metallic critical state,
$\sigma^{*}=0.3253(12)$.
