A local safety buffer can be easily wasted, since:

employees may procrastinate once they realize that they do not need the safety time

employees may not report early finishes to avoid receiving less time for tasks in the future

Instead, convert local safety buffers into global project $($and feeding buffers$)$

Take the safety time out of $$local$$ task duration estimates and aggregate these buffers into a global buffer

When doing this, use $50\%$ estimates for task lengths