A transport line ID must never map to multiple routes
Summary: If variations exist, enforce explicit suffixes to avoid confusion.
A transport line ID must never map to multiple routes
Why this matters
If “Line 1” sometimes goes to destination A and sometimes to destination B, the user is forced to check the destination every single time. This creates anxiety and errors.
Principle
One ID = One Path. If a line has branches, use explicit variations like “1A” and “1B” or simply different numbers. The route should be inherent in the identifier.