The only data on coalescence consisted of the number of cracks that coalesce, and the lengths of such cracks at observation times before and after coalescence. It would be interesting to have some spatial data, and would allow a more thorough and profound analysis. This was not available, however. Hence, a model for the rate of crack coalescence was developed. An inspiration for modelling the phenomenon in this fashion was a statistical analysis of damage accumulation in orthopaedic hip replacements [29].