The new rule, introduced in May, allows local authorities and the New Zealand Transport Agency (NZTA) to issue operators permits to run trucks up to 50 tonnes, six tonnes heavier than the standard 44-tonne limit, on specific routes.
The permits are issued at the discretion of road-controlling authorities.
Access to local roads is authorised by councils, while NZTA issues permits for state highways.
In Otago-Southland, 50 operators had, by last week, applied for the permits.
All but four were denied as NZTA assessed whether 11 bridges on State Highway 1 between Oamaru and Dunedin could take heavier loads.
NZTA regional director Bruce Richards confirmed the assessment was finished, the bridges could take the loads, and operators were free to apply for permits.
On the time lag between the new rule taking effect and the assessment being done, Mr Richards said NZTA first needed to understand which routes transport operators wanted to use.
The new rule was introduced so the country could start getting the benefits of having so-called high-productivity motor vehicles on the road rather than waiting for the entire network to be assessed.
The specially permitted heavy vehicles were no higher or wider than heavy vehicles already on the roads, but the larger loads should mean fewer trucks on the roads, he said.
Proposed routes would also affect local roads so local councils needed to be part of the process.
It took two weeks for one bridge consultant to check each bridge and recalculate its carrying capacity.
No strengthening work was required to bring the highway between Dunedin and Oamaru up to the required standard.
Instead, new modelling methods gave a more comprehensive picture of carrying capacity, he said.
New Zealand Road Transport forum chief executive Ken Shirley said operators would be relieved NZTA had now removed an impediment to developing commerce.
Some operators felt NZTA was too cautious when assessing its bridges, under-rating their capacity to protect them rather than maximising their utility.
He understood NZTA needed to understand which routes operators wanted to use, but said that "State Highway 1 between Oamaru and Dunedin - well, that is one of the big ones".
New Zealand Road Transport Association region five manager Dave Potter, who was recently critical of the delay, said it was good news the permit applications could now be processed and the NZTA had "done a great job in a short time".
Auditor-general Lyn Provost last month issued a report recommending NZTA improve the quality of information it had about bridges and tunnels, and more systematically focus its planning for maintenance and renewal work on the most important areas.
In response, an NZTA spokesman said the agency was working to address the issues raised in the report by the end of the financial year.
