There will be a trim brake (probably magnetic) to bring the speed down, followed by a block brake (mechanical) which is capable of actually stopping the train. Once a train enters this block brake, the chain lift will be declared empty and allow for the train in station to depart.
Once the station train has departed, it marks the station block as empty and the block brakes release the train to roll around into the station. The station is now occupied, the chain lift is occupied but the block brake is empty. Only in these conditions will the chain lift take the train entirely to the top and allow it to crest the hill. Once this train reaches that block brake again, the chain lift is then declared empty again and the cycle goes on...