This is the 4672nd most frequent Russian word.
достигнув
Having achieved or reached.
This uses 'достигнув' as a verbal adverb showing a completed action preceding the main action.
Достигнув вершины горы, путешественники устроили привал.
Having reached the mountain's summit, the travelers took a rest.
Here, 'достигнув' illustrates a completed action leading to an emotional response.
Достигнув цели, он почувствовал облегчение и удовлетворение.
Having achieved his goal, he felt relief and satisfaction.
In this sentence, 'достигнув' denotes the completion of the train's arrival prior to the opening of the doors.