The adverbial pronoun y is standing in for à + [destination] in this example: https://french.kwiziq.com/revision/grammar/the-adverbial-pronoun-y-means-there
The point is that you can't say : ... mais finalement je suis allé à pied.
I hope this helps, Bonne continuation !
Sign in to submit your answer
Don't have an account yet? Join today
Test your French to the CEFR standard