Service type looks like a billing label. It is actually the backbone of the schedule.
Why it matters
Almost every planning rule needs to know the type before it can decide anything. Duration comes from it. Licence requirements come from it. Whether the visit can be moved a week, whether it needs interior access, whether it can share a route with reactive work — all of it follows from the type.
Where types are coarse, every downstream rule has to be coarse too. An operation with one type called “Service” has to guess at durations, and guessing at durations is how finish variance is born.
How you notice it slipping
Several types mean the same thing because they were created by different people. One type covers jobs that take twenty minutes and jobs that take two hours. The list has grown to forty entries, so nobody can pick reliably and the data stops being comparable.
What to do
Keep the list as short as the real differences require, and make sure each type carries an honest duration and a clear requirement for who may perform it. Review the list once a year; it grows quietly, and a tidy list is the cheapest planning improvement available.