A "castles in the sky" plan by the NSW government to convert 8000 diesel-fueled buses in Sydney to electric power has been delayed by five years.
After the ambitious idea was proposed by former transport minister Andrew Constance in 2019, the government began work to transition diesel and gas buses by 2030.
The project now has a revised completion date of 2035 for all buses in Sydney, Infrastructure Minister Rob Stokes told a budget estimates hearing on Tuesday.
"It's good to build castles in the sky then go about building foundations underneath them," Mr Stokes said, when asked about the plan's viability.
"That's exactly what we're doing in the final business case."
Once the Sydney bus changes are completed the government will move on to regional buses and expects all of the state's buses to be electric by 2047.
There are 103 electric buses in NSW, and another 100 have been ordered, Transport for NSW Secretary Rob Sharpe said.
The government's most recent electric bus purchases came at a cost of $70 million for 79 buses.
Asked if the plan was now to have a fleet of about 1100 electric buses - 6900 fewer than originally anticipated - Mr Stokes said details were still being determined.
"Certainly, my aspiration would be to do everything we can to get there even quicker than (2035)," he said.
Decisions would be made after the business case was completed, he said.
Transport Minister David Elliott recently criticised his predecessor for setting such an ambitious target.
"There's no way in the world we're going to meet that timetable, so I don't know why he (Mr Constance) said it," Mr Elliott told budget estimates last month.
"I'm committed to it .... (but) I'm not committed to the time frame that my predecessor offered up."
Mr Stokes said he would choose a more charitable form of words.
"I certainly think he put out a bold goal," he said.
"We're going to reach their target a little later than he suggested."
The government is committed to replacing the buses in inner Sydney by 2035, in the regions by 2040 and the remainder of the fleet by 2047, Transport for NSW Deputy Secretary of Infrastructure and Place Camilla Drover told the hearing.
The department was using its current budget allocation of $218.9 million over seven years to purchase buses and build electricity infrastructure, she said.
Further assurances about the program's completion could not be made until the business case was finished.
Mr Stokes also addressed the government's apparent interest in flying cars - referred to in a draft version of a 50-year blueprint for the state's future transport strategy.
The final document made reference to emerging technologies allowing electric and hydrogen vehicles a vertical takeoff, which it said could potentially form a more personalised, faster form of transport.
"I certainly think we need to be open to what the technology of the future could offer," Mr Stokes said.
"I don't anticipate that we'll be flying around in cars anytime soon."
Mr Stokes also affirmed the government's commitment to fast rail but said he understood there was public scepticism around the issue.
The government committed $500 million to upgrade the rail line between Newcastle and Sydney via the Central Coast in its last budget, and is hoping for further investment from the Commonwealth.
Mr Stokes said the upgrades were needed to enable possible fast rail in NSW in the future.
"That's the first piece of the puzzle," Mr Stokes said.