How do you manage braking action for the last third part of the runway as no aircraft experienced it?

Indeed, the last third part of the runway is not often reached by the aircraft. However, aggregating additional input source data, Run[waiz] can provide a full assessement through all thirds.
But not only ! Aircraft braking action can be extrapolate to the untouched third thanks to a dedicated forecast algorithm based on other experienced by aircraft thirds, and other input data status on the last third.