Sydney’s M4 motorway tunnel, part of the WestConnex, was closed westbound early Thursday due to fears the concrete roof might collapse. Transport for NSW reported the closure happened around 6am between Haberfield and North Strathfield, calling it "emergency roadworks." Howard Collins, Transport for NSW coordinator general, said Transurban found large bulges in the tunnel’s shockcrete during an overnight inspection. Shockcrete is sprayed concrete separating the tunnel from a waterproof layer and sandstone above. "The engineers … who were working for Transurban last night discovered a couple of large bulges in the tunnel roof. And quite rightly, for safety reasons, they were concerned that if there was a major issue with this shockcrete, it could fall on vehicles," Collins explained. By Thursday afternoon, one of three lanes was reopened. However, Transurban requested another full closure from 10pm to continue repairs. NSW roads minister Jenny Aitchison said drivers reported delays up to two hours, with some stuck for four hours inside the tunnel. She blamed the delays on “a failure of privatisation” and criticized Transurban’s poor communication during the morning peak. Aitchison added that Transport for NSW had offered technical help, but Transurban initially refused assistance. Transurban’s WestConnex general manager Denise Kelly apologized for the impact and confirmed maintenance overnight aimed to reopen all lanes by Friday morning. The government is negotiating with Transurban, which owns major private motorway tolls including WestConnex, to unify tolling in NSW. Aitchison said Transurban promised to refund tolls charged during the disruption. Collins said that before reopening fully, Transport for NSW needs assurances about the tunnel’s structural safety. He said if the problem is just the waterproof membrane and shockcrete, Transurban will remove these to prevent hazards. Collins noted it was ironic that Transurban’s toll machines provide detailed data on delays, helping NSW understand the problem’s timing and severity.