Most of the decisions that have made New Zealand an efficient economy are made one step away from politics, by agencies appointed to keep their eye on the national interest. None is more important than the NZ Transport Agency.

Its new chairman, Sir Brian Roche, fills a vacancy left by Michael Stiassny who quit in April — just a year into a three-year term — for reasons that were not well explained.

Stiassny is credited with uncovering and repairing the agency's failings in regulating issuers of vehicle warrants of fitness. He told media his work was done, having "repositioned"