  We study the evolution of Abelian-Higgs string networks in large-scale
numerical simulations in both a static and expanding background. We measure the
properties of the network by tracing the motion of the string cores, for the
first time estimating the rms velocity of the strings and the invariant string
length, that is, the true network energy density. These results are compared
with a velocity-dependent one scale model for cosmic string network evolution.
This incorporates the contributions of loop production, massive radiation and
friction to the energy loss processes that are required for scaling evolution.
We use this analysis as a basis for discussing the relative importance of these
mechanisms for the evolution of the network. We find that the loop distribution
statistics in the simulations are consistent with the long-time scaling of the
network being dominated by loop production. Making justifiable extrapolations
to cosmological scales, these results appear to be consistent with the standard
picture of local string network evolution in which loop production and
gravitational radiation are the dominant decay mechanisms.
