Coverage is the metric, not distance
A distribution route is evaluated on outlets served, not kilometres run. Two routes covering the same distance can differ enormously in how many outlets were actually worked.
What is worth recording per outlet is arrival time, dwell time and whether a transaction occurred. Dwell time is the revealing one: a two-minute stop at an outlet that needs ten did not do the job.
Comparing dwell time across routes for similar outlet types is what separates territory difficulty from salesman behaviour.