There will be major delays to peak-hour train services on the Cranbourne train line after a woman in her 70s was killed as she crossed train tracks in Melbourne's south-east.

Trains were replaced by buses between Westall and Dandenong on the Cranbourne/Pakenham line after the woman was killed by an express train at a level crossing in Springvale shortly after 3pm on Tuesday.

Metro said that while trains had resumed running around 5.45pm there would continue to be major delays.

"We are still anticipating major delays of 30 minutes as we get drivers back in position to run services," Metro said.

Police believe the woman was crossing the tracks at Springvale Road when she was struck by a city-bound express train.

Emergency services were called but the woman died at the scene.

Vicroads said Lightwood Road, Springvale had reopened around 5.45pm after being closed due to the incident.