Push for investigation into safety, durability of Great Western Highway's historic Convict Bridge
Damage to the road surface has closed a section of the Great Western Highway. (Supplied: Transport for NSW)
In short:
A Blue Mountains group has been lobbying the government to investigate the safety of Convict Bridge, which has now forced the closure of a critical link between Sydney and western NSW.
The Great Western Highway has shut at Victoria Pass indefinitely, causing thousands of motorists to take an alternative route.
What's next?
A timeline for reopening remains unclear while geotechnical engineers work to determine the cause of the damage.
A Blue Mountains community group has been warning the New South Wales government the almost 200-year-old Convict Bridge on the Great Western Highway was unsafe.
Now it is moving and cracking.
Convict Bridge was built in the 1800s and remains a vital piece of the highway linking Sydney and the state's west.
It is used by approximately 12,000 motorists each day.
Blackheath and District Chamber of Commerce wrote to the state's Regional Transport Minister Jenny Aitchison in December pointing out the real possibility the historic structure could fail due to the pressures of 21st century transport.
Since then the government installed sensors to monitor the bridge.
That equipment has now detected unsafe movement, forcing the closure of one of the most important freight and transport links in NSW.
The road has been closed indefinitely between Lithgow and Mount Victoria, forcing traffic onto the alternative Bells Line of Road.
Convict Bridge was built 194 years ago and was designed for horse and carriage. (Supplied: NSW State Archive)
Chamber of Commerce president Michael Paag said if the government had acted on its earlier warnings about the fragility of the nearly 200-year-old bridge the closure could have been avoided.
"It's the most critical link between Sydney and the Central West and we can't afford to have that link broken as we have now," Mr Paag said.
"It was designed for horse and cart and it's carrying probably 1,800 truck movements a day. Those trucks weight anything up to 50 tonnes, plus thousands of car movements."
A letter addressed to Ms Aitchison on December 19, 2025, requested, in addition to the sensors, a structural investigation to determine the durability, resilience and remaining life span of Convict Bridge.
"[Transport for NSW] must … acknowledge the real possibility of failure," stated the letter from Blackheath and District Chamber of Commerce.
"The structure's engineers and builders, who back in 1825 could in no way foresee the present speed and load pressures being placed on the bridge."
The group said its request had gone unanswered.
The road winds through the steep Hartley Valley. (Supplied: David W Noble)
Timeline of events
Routine monitoring of the site up to Thursday morning had failed to pick up damage.
In a timeline of events sent to the ABC by Transport for New South Wales, the department said a visual inspection of the road by a staff member on Thursday found no issues.
"[The inspection was] of a series of "plugs" in boreholes that had been drilled into the road surface for previous geotechnical assessments," the department said.
"Later that evening, staff called to assist a heavy vehicle that had broken down on Mitchell's Causeway saw that one of the plugs had dropped about 20cm.
"This was reported to geotechnical staff, who carried out further assessment and found an existing crack in the road surface had increased significantly in size."
Transport for NSW said that led to the decision to close eastbound lanes of the highway on Thursday night.
On Sunday, new defects were discovered by geotechnical crews, including movement of the road substructure in the westbound lane, forcing the closure of the highway entirely.
TfNSW is currently working to determine the cause of the damage and said there was no suggestion a single heavy vehicle was the cause.
The road closure is having major impacts on motorists travelling between Sydney and the Central West. (ABC Central West: Lani Oataway)
Fragile but critical road network
The closure has put a spotlight on how fragile the road network between Sydney and the Central West is, renewing calls for a shelved multibillion-dollar Great Western Highway tunnel to be reconsidered.
Transport for NSW's Sydney to Central West Corridors White Paper, published in February 2026, highlighted significant issues the Victoria Pass posed to the reliability of the Great Western Highway.
It was labelled "a complex maintenance and resilience issue that needs attention".
"It affects people trying to get to work, it affects children trying to get to and from school, it affects people trying to get to their medical appointments," Mr Paag said.
"It's going to have impacts on how long goods take to get to Sydney and the Central West, and it's ultimately going to have an impact on the cost of freight."
The Great Western Highway is shut from Lithgow, with access allowed to residents only. (Supplied)
There are concerns the Bells Line of Road, currently being upgraded, is an unreliable alternative that can be shut by a single motor vehicle accident or adverse weather.
"The Central West could essentially be cut off from Sydney by road,"he said.
"Hopefully they can do some repairs, otherwise we're going to be in for a lot more pain."
The state's peak trucking organisation, Road Freight NSW, has warned major projects may be delayed because of the highway's closure.
Machinery such as cranes, pipes and energy storage systems require a permit to travel on other routes and it can take weeks to make alternative arrangements.
There are visible cracks and movement has been detected on the Convict Bridge near Little Hartley. (Supplied: Transport for NSW)
During NSW budget estimates on Tuesday, Ms Aitchison said the timeline for reopening remained unclear and relied on two factors.
"Safety first, and then making sure we can get a long-term fix on that road rather than trying to get it open for a quicker result now which will have a longer term impact for the community," the regional roads minister said.
She said the Minns Labor government had spent $20 million repairing damage to the slope that occurred during the 2022 floods.
Matt Fuller from Transport for NSW told budget estimates the Victoria Pass slope had been identified as "high risk".
"We've been accelerating some of the investigations and monitoring over some time commensurate with the age of the infrastructure around the highway [and] the sensitivity in the area," Mr Fuller said.
"That range and that crossing has been under very close monitoring for some time."
Geotechnical engineers are currently on site 24/7, working six-hour rotating shifts.
The ABC has contacted the state's transport minister and Transport for NSW for comment.