Underneath one of south-west Sydney’s busiest roads lies the city’s first koala underpass.
At 52 metres long, the Glen Lorne crossing cost $12 million and was designed to reduce vehicle strikes and deaths for one of the state’s last disease-free koala populations.
Transport for NSW estimates around 10,000 vehicles use this section of road each day.
But since the underpass opened to wildlife five months ago, not a single koala has been recorded using the safe passage.
The Sydney Basin Koala Network says more than 50 koalas have been killed in vehicle strikes along Appin Road since 2022. (Supplied)
That came as no surprise to environmental researcher and policy analyst Colin Salter, who said studies of underpasses in northern NSW and Queensland found koalas rarely used them.
“[These studies] used wildlife cameras within the underpasses themselves as well as outside the structures,” said Dr Salter, who also works as WIRES policy lead.
“While there are records of koalas using them, there are not many, and they are infrequent … like one or two detections.
“But the research has also said that there is not enough data, even though there are repeated results from different studies that show there’s a low use by koalas.”
Colin Salter says there have been few recorded sightings of koalas using underpasses. (ABC News: Simon Avery)
In 2022, researchers from the University of Southern Queensland spotted only one koala and a handful of native animals using crossings under the Toowoomba bypass throughout a 12-month study using camera traps.
This was similar to Southern Cross University’s 2021 study, which detected close to 5,000 medium-to-large mammals and goannas using highway underpasses at Port Macquarie and Grafton.
Dr Salter said studies showed it could take a “significant period of time” for wildlife to start using new crossing structures.
Overpasses preferred
Dr Salter said overpasses were a more effective way to protect animals from vehicle strikes.
“There appears to be a preference for overpasses as they are wildlife crossing structures that replicate habitat,” he said.
“There’s research in Australia, but also internationally, which shows this.”
The NSW government told the ABC it had not considered an overpass due to the topography of the land, the environmental impacts it would have had and the disruption that would have been placed on Appin Road.
Dr Salter said although it was a disappointing decision, the underpass could help fill important knowledge gaps.
“The [underpass] is the approach the government has adopted, so we just have to hope it’s going to work,”
he said.
“It provides us with a significant opportunity to monitor the movement of animals on either side of the underpass in the adjacent habitat, but also if they are moving towards and through the underpass.”
Cameras installed at the underpass will be used to improve koala safety and habitat connectivity. (ABC Illawarra: Justin Huntsdale)
The box-culvert structure was delivered by developer Stockland, which is building the neighbouring 1,700-home Figtree Hill Estate.
Construction of the crossing was held up while Stockland sought access to Lendlease-owned land on the opposite side of the road.
The Sydney Basin Koala Network (SBKN) said BioNet data showed there had been six koala strikes and five deaths during the delay period, which Stockland described as “regrettable”.
SBKN said 66 koalas have died on Appin Road since July 2022.
More Appin Road underpasses 
Environment Minister Penny Sharpe (centre) describes the completion of the Glen Lorne koala underpass as “historic” and “really important”. (ABC Illawarra: Justin Huntsdale)
Stockland is now due to build another Appin Road underpass near the Beulah Nature Reserve.
NSW Environment Minister Penny Sharpe said she wanted to avoid the delays that left the Glen Lorne crossing almost a year behind schedule.
Stockland is to deliver Glen Lorne and Beulah underpasses while the state government will build Ousedale. (Supplied: Transport for NSW)
“Sometimes delays happen. I still think this is absolutely worth it,” she said.
“Hopefully the lessons that we have learnt here will see works sped up.
“I understand why people are concerned about it as it is a precious koala population.”
The developer has told the ABC it has secured a land access licence with Lendlease to facilitate Beulah’s delivery and that environmental applications would be lodged in the coming months.
The final Appin Road underpass, Ousedale, is a Transport for NSW project slated for the end of 2027.
Editor’s note 03/09/2026: This article has been modified to reflect that the NSW government did not reject a proposal for an overpass to be built, as no formal proposal was made.
Glen Lorne koala underpass at Noorumba Reserve is supported by around 3km of koala exclusion fencing along both sides of Appin Road. (ABC Illawarra: Justin Huntsdale)