Crossword clue: Big name in "vertical trains"

The answer "OTIS" fits the clue because Otis is a well-known company that manufactures elevators and escalators, which are often referred to as "vertical trains." These machines help people move up and down in buildings, just like trains move along tracks. The name Otis has become synonymous with elevators, making it a big name in this industry. Therefore, it perfectly matches the clue about "vertical trains."