Thomas the Train: TrackMaster Runaway Boulders
As Mavis approaches the Quarry she will activate the boulder that is on a cliff above her. The boulder will then roll down the mountain and jump over Mavis and the track. A crossing arm will then drop down in front of Mavis (stopping her) while the boulder passes in front of her. The crossing arm insures that Mavis will not crash into the boulder. The child can now lift the crossing arm and Mavis can be on her way safely.