Why use indicative passe simple? (sorry can`t insert an accent).

Question

Elle courait quand le bus arriva. Arriva to my knowledge is not spoken, therefore would this be the format in a written report?

Accepted Answer

Bonjour James !Elle courait quand le bus arriva.You are correct if assuming that this is more of a written sentence than a colloquially spoken one. The use of Le Passé Simple here makes it look as part of a written story, and indeed in everyday speech, you'd use Le Passé Composé:Elle courait quand le bus est arrivé.(Though Quand le bus sera arrivé, elle courait. makes no sense here -> When the bus has arrived, she was running.)I also agree that using Le Passé Simple here is confusing, and I therefore changed the example to the second option :)Merci et à bientôt !

Answer

Bonjour James,
While all of us that are native English speakers are striving to learn French, it appears to me that the lesson goal is the imparfait and not the passé simple. Elle courait quand le bus arriva.
She was running when the bus arrived.   To that end, I do think you have a valid point; why use the  passé simple for the clause.  It seems that a more appropriate phrasing would be:
Elle courait quand le bus est arrivé, or Quand le bus sera arrivé, elle courait. 
Je suis d'accord que cette leçon est un peu ambiguë.
Peut-être la leçon serait modifié.
J'espère que cela vous aidera.
Bonne chance !

Answer

Merci Aurelie,
I have just got my head around using the future tense with `Quand`. 
Quand tu viendras, tu verras la nouvelle cuisine.
When you come, you will see the new kitchen.
Notice how in French you use the Le Futur in both parts of the sentence, including after quand, whereas in English you use the Present tense after when.
The lesson we are discussing is, of course, using the imperfect tense in a continuous action.
It could be an easy trap to fall into, using the future instead of the imperfect.
A bientot.