Many on the left claim that the PPP model used for Transmission Gully is responsible for the fact it opened late, and cost more than budgeted.
But I think that is ideology speaking, not analysis.
So I saw an article this week on the Auckland City Rail Loop (which is not a PPP) and thought it would be useful to do a comparison.
The CRL was estimated to cost $2.5 billion and then up to $3.4 billion when funding was finalised.
Then it rose to $4.4 billion and no one expects it will stay at that level.
But already it has cost 76% more than first budgeted. It will probably end up at over $5 billion.
Transmission Gully went from $850 million to $1.25 billion – a 47% increase, and that is final.
The lesson is Government often under-estimates the cost of construction projects. This is not unique to ppps.