Holden has back-flipped on selling its iconic Lang Lang test track, confirming the top-secret facility will remain operational even after the company closes its manufacturing plants by 2017.

The Aussie car maker confirmed today that it will maintain its local engineering division beyond 2017 as an outpost of its parent company, General Motors.

The decision means Holden will continue to play a significant role in the development of GM's global product portfolio, building on the decision to maintain its Australian design centre.

It has yet to confirm precisely how many engineering jobs it has saved as a result of the decision, but the company expects to maintain a Victorian workforce of around 200 employees across the design centre and test facility - significantly less than current count of around 1000.

Holden could also not confirm yet if Lang Lang will maintain all of its current facilities, but it is likely to be reduced after Commodore production ceases.

What it did say was the facility will remain operational to ensure future imported vehicles sold by Holden will maintain an "Australian accent" and that its primary role will be to tune cars specifically for local conditions.

"Whether it’s earned on the Proving Ground or created in the GM Australia Design Centre, Holden will keep its proud Australian identity,” General Motors' President for International Operations Stefan Jacoby said today.

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“This announcement means that post-2017, Holden will not only retain its Lang Lang Proving Ground in Victoria but will host a design, engineering and product development workforce in Australia.

“This is an important step in ensuring that Holden and its products continue to speak with a strong Australian accent now and in the future. The world over, everything starts and ends with great product.

“Our continued investment in the Proving Ground and the GM Australia Design Centre reinforces the strength of the Holden brand and the company’s commitment to maintaining a significant presence in the Australia.

“The Australian design and engineering capability is also a critical asset for GM globally. This local team is a key part of our global design and engineering strategy for the future.”

The Lang Lang facility has been developed over time into one of the most advanced facilities of its type in the southern hemisphere. Within its secured boundaries – which have regularly been pierced by photographers looking for scoop images - it has more than 44km of road systems, including a network of sealed tarmac and dirt roads to evaluate the comfort and handling of vehicles before they go on sale, rough roads to accelerate rattles and squeaks for long-term durability, mud and water baths to test the sealing properties of doors and windscreens as well as a circular banked track for high-speed driving.

Holden claims it is an “oasis of natural vegetation” and that around 75 per cent of it 2167 acres has been undeveloped leaving a “mixture of regenerated and undisturbed bushland habitat of high conservation significance.”

It had been independently valued to be worth approximately $20 million when Holden indicated it was going to sell the facility late last year.Holden says it also has “Australia’s most comprehensive safety test centre and a high-tech exhaust emission facility capable of conducting a wide range of vehicle exhaust emission tests to Australian, USA, European and other international requirements.”

Arch rival Ford also has an advanced proving ground operation at the You Yangs, between Melbourne and Geelong.

The facility will similarly remain operational to assist with the development of future vehicles for the blue oval’s global portfolio after Ford closes its Broadmeadows and Geelong manufacturing factories in 2016.