The workplace health and safety regulator has lifted a prohibition notice on the Kapiti miniature railway, north of Wellington.
WorkSafe New Zealand closed the railway in December last year after an engineer's report found significant safety flaws in the Raumati Beach model railway including unstable carriages.
The report followed an accident in September, when a family tipped out of a train as it rounded a bend.
Chief Inspector Alan Cooper said the operators have addressed the immediate safety concerns of Worksafe New Zealand, and the railway can now continue operations.
He said an engineer's inspection on Thursday was satisfied the key issues have been dealt with and WorkSafe New Zealand will work with the operators to ensure its safety plan is implemented.