The clock starts at the first collection
The quality question in dairy is not distance, it is elapsed time from first collection to chilling, and it applies to the whole load rather than the last village.
Measuring that per route rather than per vehicle is what exposes the problem, because a route that runs twenty minutes late every day compounds across every collection point on it.
Once measured, the fix is usually sequencing rather than speed: which village goes first, and where the route doubles back.