To achieve that it proposed allowing greater balance sheet flexibility for the the National Land Transport Fund or the agency itself "through access to additional finance".
A current priority for the agency is the $9 billion roads of national significance programme which the Government sees as a key plank in its economic development programme.
But early this year the Transport Agency warned Mr Brownlee that funding constraints could delay completion of the programme by three years to 2024.
Green Party transport spokeswoman Julie Anne Genter said the Government was "facing a growing funding gap between stagnant road tax revenue due to declining road use and the rising costs of its uneconomic motorway programme".
Ms Genter said additional borrowing by the Transport Agency and "back door borrowing" in the form of public private partnerships meant the Government was putting the cost of the new roads "on the nation's credit card".
But Mr English said the effect of any additional borrowing under the new legislation on overall Crown debt was "yet to be determined".
"If there is any it will be fairly minor," he said. "It's really as I understand it giving NZTA the capacity to manage fluctuations in the roading programme and their public transport funding programme.
"If they were going into any extensive borrowing there would have to be a pretty deep consideration of all the incentives and costs that go with that and no one's really contemplating extensive borrowing."
In response to questions from Labour's transport spokesman Phil Twyford, Mr Brownlee said he could give no information about the level of borrowing by the Transport Agency over the next three years.