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O-Train Line 4 back in service after signaling issue halted operations

On-site repairs were needed as remote troubleshooting attempts proved unsuccessful

OC Transpo says service on Line 4 of Ottawa's O-train has now resumed after a signaling system issue forced them to suspend service Friday.

The transit agency posted on social media about possible delays — then about suspended service — on Line 4 around noon.

In an email, the transit agency said the issue with the signaling system first started at around 11:30 a.m. Attempts to resolve the issue remotely were unsuccessful, prompting the agency to suspend train service as repairs were being done on-site.

Transit users were told to use Route 105 bus service to travel between the Ottawa International Airport and South Keys station.

Line 4, which opened in January 2025, experienced shutdowns earlier this year, in May and June, due to staffing shortages.