Complex sentence: At approximately 5:50PM, Train 3681 departed Waban station, passed signal H-64; signal H-64 changed to display a single red aspect to indicate that Train 3681 was directly ahead of it.
Split into simpler sentences: At approximately 5:50PM, Train 3681 departed Waban station, and passed signal H-64. Signal H-64 changed to display a single red aspect, to indicate that Train 3681 was directly ahead of it.