______ when will the next train come?

The correct answer is: Thank you

The man is interrupting the other man and asking about the next train time. There must be some urgent seen in his status and so, he uses the word 'excuse me'. Excuse me means, asking sorry for their action which might have disturbed the other person and asking for help. We should not disturb anyone and anything and if we does so, we should ask be using the word 'excuse me' which will not offend the opposite party.