About a hundred carriages wait for arriving Hogwarts students along a rough, mud road near the railway station on September first each year, and take them back to the station at the beginning of the summer holidays.
They are pulled by what Harry as a third- and fourth-year student assumed were invisible horses (PA5, GF11, GF12, GF37); this was verified at the beginning of his fifth year (OP10), when he first became aware of his ability to see thestrals. The thestrals who pull the carriages are very well-trained, since they make the journey unassisted past the wrought iron gates and around the lake to the castle. The coaches smell of mold and straw (PA5). A carriage was waiting for Lupin "at the gates" when he was ready to leave Hogwarts. It is unclear whether this was one of these same stagecoaches or why it would be stopped way back at the gates (PA22).