"Free" public transport for holders of SuperGold cards could become a victim of its own success.
Figures obtained by Radio New Zealand show the budget for the scheme will be blown if rising patronage continues at its initial rate.
Figures for the four months to the end of January show public transport operators received $5.5 million from the Government for providing off-peak public transport to holders of SuperGold cards at no charge to them.
Some 2.5 million pensioners took public transport during that period.
Usage is growing by $100,000 per month, exceeding budget expectations.
An allocation of $18 million per year over the next four years was made in the 2008 Budget.
Transport Minister Steven Joyce says the scheme is within budget, but he is keeping an eye on it.
While there are no plans to scrap the scheme, he says there are also no plans to extend it in these tough economic times.