  The dynamics of string junctions and their influence on the evolution of
cosmic superstring networks are studied in full detail. We review kinematic
constraints for colliding strings in a Friedmann-Lema\^itre-Robertson-Walker
background and obtain the average distribution of possible string
configurations after string collisions. The study of small-scale structure
enables us to investigate the average growth/reduction rate of string junctions
for a given cosmic string network. Incorporating the averaged junction dynamics
into the velocity-dependent one-scale model for multi-tension string networks,
we improve the semi-analytic description and quantitative understanding of
cosmic superstring network evolution.
