  Over the past years our understanding of the scaling properties of the
solutions to the one-dimensional KPZ equation has advanced considerably, both
theoretically and experimentally. In our contribution we export these insights
to the case of coupled KPZ equations in one dimension. We establish equivalence
with nonlinear fluctuating hydrodynamics for multi-component driven stochastic
lattice gases. To check the predictions of the theory, we perform Monte Carlo
simulations of the two-component AHR model. Its steady state is computed using
the matrix product ansatz. Thereby all coefficients appearing in the coupled
KPZ equations are deduced from the microscopic model. Time correlations in the
steady state are simulated and we confirm not only the scaling exponent, but
also the scaling function and the non-universal coefficients.
