It was raining in Melbourne's CBD last Friday morning, and because it's autumn the city was scattered with leaves.

At the same time on Collins Street, just before Queen Street, a tram driver told passengers the ride would be slow for the next little while. That's because, the driver said, the tracks were slippery. It wasn't just due to rain.

Crowded tram stop at the Bourke Street mall. Credit:Joe Armao

It was because leaves had become stuck on the tracks; pressed onto the steel by the weight of the passing trams, but made more adhesive by the rain. The driver pushed on, moving slowly, only a few metres per minute.

By the time the tram stopped near William Street, many hopped off, while others remained for the tedious but necessarily careful journey toward Spencer Street. A passenger told Fairfax Media at no point did he feel the tram was in danger of slipping off the tracks, but that the driver explained this was a risk if the tram did not continue slowly.