Executives at Sydney Trains have apologised for a “terrible” morning on the transport network after a combination of problems caused massive delays across the city on Tuesday but expect the afternoon to run more smoothly.

A wiring fault at Hornsby left a train stranded near the entrance to a transport depot, which blocked a further 20 trains behind it, while a medical emergency at Erskineville caused extensive delays through Sydney’s inner west before 8am.

Sydney Trains have apologised for Tuesday morning's delays. Credit:AAP

Meanwhile, a mechanical issue near Lidcombe and a fire alarm evacuation at Town Hall in the morning rush added to delays. The incidents occurring within a few hours wreaked havoc, with services to the north, south and west all experiencing delays.

While thousands of commuters were caught up in the delays, Sydney Trains chief executive Stewart Mills said the network would likely have recovered by the afternoon rush.