Worked example · MFL: German · Year 11

Solving a German rail disruption with a flowchart

DCF: Data and computational thinking → Problem solving and modelling

What this is

A secure Year 11 response and answer key, annotated so you can see which success criterion each part meets. Key answers: at 13:35 the model chooses the ICE 277 (Gleis 8, 14:50, arrives 16:52). After the 14:40 announcement the ICE 277 would arrive at 17:32, so the model switches to the ICE 71 (Gleis 6, 14:55, arrives 16:57), with 15 minutes to reach the platform. Show this after pupils have built their own flowchart.

Step 1: reading the dossier

(a) It is cancelled today because of a repair to the train.

(b) It is about 35 minutes late, and it leaves from platform 6 instead of platform 7.

(c) The train will be very full and a seat reservation is recommended. Our ticket has no seat reservation, so we might have to stand for two hours with our luggage.

(d) At the exit by platform 1 at Freiburg Hauptbahnhof, until 17:45.

(e) Our ticket is not valid on the coach, and the coach arrives at 18:10, after Herr Becker has left for work.

(f) 1. Not tied to one train: today you can take any Deutsche Bahn train on this route. 2. I can wait until 17:45, then I have to go to work.

Every detail is picked out, including the platform change, which is easy to miss and would lose the train. Translation (f) 2 turns dann muss ich zur Arbeit into natural English (“I have to go to work”). Evidences criterion 1.

Step 2: the options at 13:35

OptionReal departure and platformReal arrival in FreiburgChangesTicket valid?By 17:45?
A: ICE 7114:20 + 35 = 14:55, Gleis 616:22 + 35 = 16:57noneyesyes
B: ICE 27714:50, Gleis 816:52noneyesyes, but very full
C: IC 2275 then RE 471514:13, Gleis 917:061, at Karlsruhe: 15:26 to 15:34 = 8 minutes, Gleis 2 to Gleis 3yesyes
D: ICE 27915:50, Gleis 817:52noneyesno
E: Fernbus14:30, Südseite18:10nonenono

The delay is added to both the departure and the arrival of the ICE 71. The change time for C is checked against the 5-minute rule. D and E fail for different reasons, and the table shows which. Evidences criteria 1 and 3.

Step 3: the flowchart

Flowchart: choosing a train when a train is cancelled Start. Input: time now, departures board, ticket rules, deadline 17:45. Loop over every connection: work out real departure and arrival; cross it off if it leaves less than 5 minutes from now, if the ticket is not valid, if the change time is under 5 minutes, or if it arrives after 17:30; otherwise put it on the shortlist. Either way, check whether there are more connections on the board and loop back if there are. When all connections are checked, choose the earliest arrival; if two are within 10 minutes, choose the punctual one, then the one with fewer changes. Output the train, platform and times and send the message. If there is new information, go back to the input. Otherwise board the train. Start Eingabe: Uhrzeit jetzt, Abfahrtstafel, Fahrkarte, Frist 17:45 Uhr Nächste Verbindung nehmen Echte Abfahrt und Ankunft = Fahrplan + Verspätung Abfahrt mindestens 5 Min. nach jetzt? Nein Ja Gilt die Fahrkarte? Nein Ja Direkt, oder Umsteigezeit mindestens 5 Min.? Nein Ja Ankunft bis 17:30 Uhr? (15 Min. Sicherheit) Nein Ja Streichen Auf die Kurzliste Noch Verbindungen auf der Tafel? Ja Nein Früheste Ankunft wählen. Weniger als 10 Min. Unterschied: der pünktliche Zug, dann weniger Umsteigen Ausgabe: Zug, Gleis, Abfahrt, Ankunft. Nachricht an Herrn Becker Neue Information? (Durchsage, Tafel) Ja Nein Ende: einsteigen

Run at 13:35: the shortlist is A (16:57), B (16:52) and C (17:06). D arrives too late; E fails the ticket check. The earliest arrival is B. A is within 10 minutes of it, but A is delayed and B is on time, so the tie-break also chooses B. Output: ICE 277, Gleis 8, departs 14:50, arrives 16:52.

Simpler than the real world: the model treats a delay as fixed, but ca. 35 Minuten is an estimate and delays often grow. That is why it demands 15 minutes of safety before 17:45. It also ignores how full a train is, so it would happily put us on a train where we have to stand.

The model has a clear input, a process, four checking decisions, a loop over every connection, a tie-break rule and an output. It works for any board, not only this one. The design choice (15 minutes of safety) is stated and justified from the real problem, and the limits of the model are named. Evidences criteria 2 and 3.

Step 4: the announcement

(a) The ICE 277 is now about 40 minutes late because of a repair to a door. Real departure 14:50 + 40 = 15:30; real arrival 16:52 + 40 = 17:32.

(b) At 14:40: C has gone (it left at 14:13). B now arrives at 17:32, which fails the “by 17:30” check. D and E still fail. Only A is left. Output: ICE 71 from Gleis 6, departs 14:55, arrives 16:57. We have 15 minutes to reach platform 6.

(c) My first version had no “has it already left?” check, so the IC 2275 stayed on the shortlist at 14:40 even though it had gone. The output was still right, but only by luck: if the ICE 71 had also been cancelled, the model would have sent us to a train that had left. I added the first decision, Abfahrt mindestens 5 Min. nach jetzt?, which also makes sure there is time to reach the platform.

The model is run again with the new input rather than guessed, and the answer includes the platform change and the time available. Part (c) finds a real error that only showed up with new data, explains why the right output hid it, and corrects the algorithm. Evidences criteria 3 and 4.

Step 5: sorting it out in German

(a) Hallo Herr Becker, leider ist unser Zug um 13:50 Uhr ausgefallen, weil es eine Reparatur am Zug gab. Wir nehmen jetzt den ICE 71 von Gleis 6. Er fährt um 14:55 Uhr ab, und wir werden um 16:57 Uhr in Freiburg ankommen. Wir warten dann am Ausgang bei Gleis 1. Ist das in Ordnung für Sie? Es tut uns leid! Viele Grüße, Cerys und Seren

(b)

TaskYou say
Report the problemEntschuldigung, unser Zug nach Freiburg fällt heute aus.
Ask for adviceKönnen Sie uns helfen? Welchen Zug sollen wir nehmen?
Ask about the ticketGilt unsere Fahrkarte für diesen Zug? Wir haben einen Flexpreis.
Ask the arrival time and thankWann kommt der Zug in Freiburg an? Vielen Dank für Ihre Hilfe!

The message is 65 words, including the greeting and sign-off, and contains everything Herr Becker needs in one go: what happened, the new train, platform, arrival time and where to meet. Past (ist … ausgefallen, gab), present (wir nehmen, er fährt … ab) and future (wir werden … ankommen), with the verb sent to the end after weil and a separable verb split correctly. The role play uses Sie throughout and welchen in the accusative. Evidences criteria 5 and 6.

If you finish early: answer to the first extension

At 14:50 the ICE 71 is 65 minutes late in total: it now leaves at 15:25 and arrives at 16:22 + 65 = 17:27. The ICE 277 arrives at 17:32 and the ICE 279 at 17:52. Only the ICE 71 still passes the “by 17:30” check, so the model says: stay on platform 6 and send one new message, for example Unser Zug hat jetzt mehr Verspätung. Wir kommen um 17:27 Uhr an.

Why this response is secure