In 2005, there were red faces all round when Transit New Zealand admitted its calculations showed $1.35 of the proposed $1.80 car toll for the Orewa-to-Puhoi motorway would be gobbled up in administration costs.

Despite these dire predictions, Labour politicians and the road builders decided to go ahead.

To the embarrassment of all involved, the road builders' predictions have, for once, been proven accurate.

Figures for the first five months of operation of the Northern Gateway Toll Road, to June 30, reveal that, on average, it cost $1.29 in transaction costs to collect each $2 car toll.

For those paying by phone, it would have been cheaper to have waved them through for free. Each $2 phone payment cost $2.70 to administer.

Not that Transit's successor, the NZ Transport Agency, mentions any of this awkward detail in its upbeat press release.

That document prefers to emphasise that road use was 8 per cent higher than forecast and 94 per cent of customers paid their toll.

"The strong demand for the road and the high level of compliance are testament to the benefits it offers to motorists," said the agency's regional director, Wayne McDonald.

"Having achieved our initial goal of getting motorists to use the toll road, we're now concentrating on refining and improving the toll collection system."

As well they might, because under the legislation establishing the system, the Government agreed that $1.13 of the $2 collected was to go towards paying for the motorway, 65c was for transaction charges and 22c would go in GST.

In its operating report, the Transport Agency says: "This means we can claim only up $0.65 from each toll to cover our operational costs."

To make up the difference between the 65c permitted transaction costs and the actual figure of $1.29, the agency has had to dig into its own pocket.

The report says the agency "expected costs associated with establishing the tolling business would be higher than this [65c] in the first years of operation".

But that rather begs the question, why did it agree to a 65c cap for each operational transaction if it knew there wasn't a hope of meeting it?

Were the road builders trying to mislead the politicians, or were the politicians and the road builders set on misleading the rest of us?