🚆 Railways & Public Transport · Sequence
Metro Smart Card Fare Collection
How a metro fare is charged with a smart card or bank card: tap in at the entry gate, tap out at the exit, fare by distance and balance update.
Drawing diagram…
What this diagram shows
- Gates decide offline in under 300 ms
- The fare is calculated from entry and exit stations
- Transactions sync to the central system afterwards
Prompt used
Metro fare sequence: at the entry gate the rider taps an NCMC card; the gate reader checks the card offline, writes the entry station and time on the card and opens. At the exit gate the reader reads the entry station, calculates the distance fare, deducts it from the card balance and opens. Both gates send transactions to the station computer, which forwards them to the central clearing system for settlement with the card-issuing bank.
Mermaid code
sequenceDiagram actor R as Rider participant EG as Entry Gate participant XG as Exit Gate participant SC as Station Computer participant CC as Central Clearing participant BK as Card Issuing Bank R->>EG: Tap card EG->>EG: Check card offline, write entry station EG-->>R: Gate opens EG->>SC: Entry transaction R->>XG: Tap card at exit XG->>XG: Read entry, calculate fare, deduct balance XG-->>R: Gate opens, balance shown XG->>SC: Exit transaction SC->>CC: Upload transactions CC->>BK: Settle fares
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