A woman has died after being hit by a three-wheeled motorised scooter in Melbourne's west.

Police say the yet-to-be identified pedestrian was struck by the scooter on Beachley Street in Braybrook just before 1pm.

A police spokesman said the scooter was on the road at the time of the collision.

The male scooter rider helped at the scene and was not injured.

The exact cause of the crash is being investigated.

AAP