  We report on a detailed numerical study of the evolution of semilocal string
networks, based on the largest and most accurate field theory simulations of
these objects to date. We focus on the large-scale network properties,
confirming earlier indications (coming from smaller simulations) that linear
scaling is the attractor solution for the entire parameter space of initial
conditions that we are able to probe. We also provide a brief comparison of our
numerical results with the predictions of a previously developed one-scale
model for the overall evolution of these networks. Two subsequent papers will
discuss in more detail the analytic modeling of the semilocal segment
populations as well as optimized numerical diagnostics.
