Sydney commuters are set for a slow start to the weekend with multiple train lines brought to a standstill by technical problems on Friday.

A raft of technical problems this morning brought multiple train lines to a standstill with some commuters waiting on platforms for more than an hour and others forced to walk into work.

The delays, which struck the north shore, eastern suburbs, north shore and airport lines, are set to continue to wreak havoc for the rest of the day.

Commuters were hit with major delays on Friday morning as trains came to a standstill with a broken down train at Central and signal delays at Wynyard.

The gridlock has forced some commuters to wait more than an hour and forced others to walk across the Harbour Bridge to get to work with some commuters reporting delays of more than 70 minutes on the north shore line.

The T1, T4 and T3, T9 and T8 lines are all held up by the signal failures and commuters are being told to expect delays for the rest of the day.

Commuters have been forced to board packed trains with some reporting record congestion at train stations.

Urgent signal repairs have been completed at Wynyard but buses are replacing services from North Sydney to Wynyard as well as some trains on the eastern suburbs line.