Mr Dolan said the authorities have serious questions to answer.
"Over 35 years ago, a barrier was erected there for a reason," he said.
"Just three to four weeks before our tragedy it was removed and there are a number of questions we, as parents, would have.
"We do feel angry because if you take something away that was there for a reason, really it should have been reinstated and that hurts us.
"It is just unbelievable to think that for a few pounds it could have been reinstated."
The Department for Regional Development's Road Service would not say why the barrier was taken away on 18 September.
A spokesperson said it would be inappropriate to comment because of an ongoing police investigation into the accident. They would not say if there were plans to replace the barrier.