Irish Rail have released a video which shows a load being carried by a truck colliding with a bridge in Dublin City Centre.
The incident briefly closed the Dart line between Connolly and Tara St while engineers have cleared the way at Amiens St.
"Had pedestrians, cyclists or motorists been on the other side of the road, people could have been killed at Amiens St this lunchtime," Irish Rail said in a tweet.
The video shows a tractor, hitting off the bottom of the bridge with two onlookers nearby.
"Know your load height for the safety of all," Irish Rail added.
A screenshot from the video. Picture: Twitter / Irish Rail