The machines boring the new Perth Airport link tunnel have made a significant breakthrough in the project, after progress stalled earlier this year.
The two machines — dubbed Sandy and Grace — have reached the new Airport Central Station, boring through the station wall at the weekend.
The machines are now about a quarter of the way through the eight-kilometre stretch of tunnel from Forrestfield to Bayswater.
"1.9 kilometres through the tunnel process and another six kilometres to go," Transport Minister Rita Saffioti said.
"A big milestone today as the two TBM (tunnel boring machines) have reached the first key station."
Both boring machines were forced to stop work earlier this year.
The first, nicknamed Grace, was stopped because of a number of ground disturbances detected during the project.
The second, Sandy, was stopped later when it caught up to Grace, which was still halted until an investigation into the disturbances was complete.
Both machines resumed work in April.
Ms Saffioti remained confident the project was on track for its expected completion in late 2020.
"The tunnelling (is expected) to finish at the end of next year," she said.
Both machines will receive maintenance at the new station, before resuming work in about a month.
