"Since then, given the information that I, and the public, became aware of this week around the agency's performance, it is appropriate to ask for external advice on NZTA's regulatory performance," Twyford said today.
"I have formally instructed the Ministry of Transport to review NZTA's regulatory performance. There are a number of issues that need to be addressed to provide assurance to me, and the public that deficiencies around NZTA's regulatory performance are identified and addressed, and that is why we are asking for advice on what changes to the regulatory function are required."
The review is due to be completed by the end of March next year.
NZTA board chairman Michael Stiassny told RNZ yesterday Ball's death was a "horrific event" but warned the Dargaville case would not be the end of revelations about the agency's regulatory failings.
"We've made it abundantly clear there will be more," he said.