"The agency is investigating options to improve the performance of the bridge railings, however, the original design of the structure limits the amount of strengthening work we are able to carry out on the railings to improve their performance," he said.
Campbell said as was the case with all serious crashes on state highways, the agency and the police Serious Crash Unit would investigate.
The Bay of Plenty Times inquired about any recommendations arising from previous investigations into the safety of the bridge following the 2013 crash but Campbell said the agency was unable to comment on "detail of previous crash investigations in the given time frame".
When asked whether a cause for the crash had been identified, a police media spokeswoman said it was still under investigation.
Police were appealing for witnesses to the crash but so far no one had come forward, she said.
Joint Road Safety Committee chairwoman Margaret Murray-Benge, a Western Bay District councillor, called the crash "tragic" but said the bridge was no less safe than any other in the region.
The committee had not received any complaints from residents regarding the structure of the bridge or the traffic flow, she said.
"We've never heard of any issues relating to the bridge at all."
Residents have previously told the Bay of Plenty Times the bridge was quite narrow with a small margin for error.
The bridge and highway were closed for most of Saturday and the rails lining the bridge were left smashed through.
Police divers searched the harbour near the bridge on Sunday morning before a crane pulled the ute from the water.
Security footage found by police showed a vehicle had collided with the bridge but did not show whether it had plunged into the water or had driven off.
Police would like anyone who has any information about the April 27 collision to urgently call the Tauranga police station on 07 577 4300.
