Whangarei's iconic but problematic Te Matau A Pohe bridge was peer reviewed by a firm with no experience in bascule - or lifting - bridges.
The admission is within a "Lessons Learned" portion of a Whangarei District Council response to a New Zealand Transport Agency (NZTA) report which highlights problems with the $33 million bridge.
But in general, it says the bridge has achieved its transport objective.
The WDC used a "reputable structural firm" to peer review the bridge, but the firm had no experience with bascule bridges, the report notes.
Using a firm with experience to review the project before construction may have prevented the bridge jamming shut in hot weather, the council response said.
WDC roading manager Jeff Devine said the "sticking" of the bridge was still being investigated, but it had not significantly affected traffic.
The NZTA report followed the agency's $14.6 million investment in the bridge. It also observed that congestion arose at the Riverside Dr roundabout after the bridge opened.
A two-lane roundabout had been originally planned as part of the bridge/roading project, but it was made smaller to save money. Mr Devine said this was largely due to a cap on the amount of NZTA funding available.
Construction of a bigger roundabout is planned in about 10 years.
Despite the queues, peak travel times had still reduced, Mr Devine said.
After construction was completed, the council spent about $20,000 fixing the hot weather fault as well as $354,000 adding a "slip lane" at the intersection of the Dave Culham and Riverside Drive roundabout in April.
Overall, the NZTA report said it achieved its objective of substantial reductions in the travel time between Riverside Drive and Port Rd and less traffic uptown around the Dent St intersection, with some commuters cutting up to 16 minutes off their journey times.
Whangarei had also been enhanced through the creation of a new icon.
"The design of the project is culturally sensitive, and although not strictly a transport benefit, the bridge is also aesthetically pleasing ... and now represents a popular visitor attraction."