Australian footage released today shows how important it is to keep an eye on children at the train station, especially when boarding and alighting.

A video from the security camera on one of Sydney's train platforms documents the critical minutes when a mother with a baby in a carriage and a 4-year-old boy wait for the train to reach the platform.

The boy, excited to board the train, left his mother's hand and walked forward carelessly, without noticing the gap between the cab and the platform - and fell in.

The mother, who noticed immediately, waved her hands to other passengers to signal the train driver not to go. A number of other people at the station rushed to extract the child, without his being injured.

Sydney iStock