A tram driver who crashed through a bus shelter and hit a fire hydrant in Ascot Vale early on Tuesday morning has told police that he fell asleep.

The 49-year-old driver said he was asleep at the wheel when his tram slammed into a traffic light pole, damaging overhead lines and creating peak-hour traffic chaos for the morning in the city's north-west.

Sergeant Jason Doyle said the driver, from Sunshine, is expected to be charged with careless driving.

''My understanding is he admitted falling asleep and he's lucky he didn't kill anyone.''