Luas drivers testing the new Cross-City line are being blocked by cars and delivery vans.
Trams are traveling the new route to iron out any problems before passengers get on board later this year.
Testing will be up to every 20 minutes from Monday.
Graeme McQueen is from Dublin Chamber. He says there has been a few hiccups.
"There was a couple of incidents yesterday on Dawson Street in particular, where delivery trucks were sat on the lines.
"It just was stopping the testing from taking place.
"I think the message to everyone is if you are delivering something to make sure that the parking has been done in the right places".