The company that operates nearly all of Sydney’s toll roads will be allowed to push ahead with its bid to buy a controlling stake in the city’s mammoth WestConnex motorway.

Transurban was given the green light by the competition watchdog on Thursday after agreeing to publish traffic data that could help rivals bid for future toll road projects and potentially give taxpayers and motorists a better deal.

The decision will be welcome news for the NSW government, which wants to finalise the sale of the $16.8 billion project before the March 2019 state election.

Australian Competition and Consumer Commission chairman Rod Sims said the offer of high quality traffic-flow data allayed the regulator’s concerns about the impact on competition.

Information about what type of vehicles pass through the gantries and how much is paid can be used to validate bidders’ models, which are used to secure finance.

Transurban, Australia’s 13th largest listed company, already controls seven of Sydney’s nine toll roads.

WestConnex will extend 33 kilometres from Parramatta to the South Western Motorway mostly via tunnels under the inner suburbs.

Mr Sims said more competition for toll roads could see tolls reduced for drivers.

‘In that sense, we think this undertaking can benefit drivers through lower tolls into the future,’ he told reporters.

He suggested state governments consider requiring similar data be provided when running tenders for future projects to maximise competition and get the best results for taxpayers and motorists.

‘They need to make the trade-off between maximising one-off revenue and the level of tolls into the future for drivers,’ Mr Sims said.

He also warned governments against accepting unsolicited proposals for new toll roads to ensure healthy competition and that drivers weren’t paying more than they should.

It’s understood the government has received two bids for WestConnex – from a consortium led by Transurban and investment group IFM.

Treasurer Dominic Perrottet said the NSW government will continue to assess the bids based on all available information and will not comment further.

An announcement on the outcome will be made in ‘due course’, he said in a statement.