The Amtrak Speedster is a high-speed train service offered by Amtrak, the national rail system in the United States. The four crossword solutions associated with this term are Acela (5 letters), CHEETAH (7 letters), HARE (4 letters), and REOS (4 letters). Acela is Amtrak's flagship high-speed train service, offering speeds up to 150 mph. The CHEETAH is a high-speed train that was introduced in the late 1990s and can reach speeds of up to 125 mph. The HARE is a regional train service that operates at speeds up to 110 mph. Finally, REOS stands for Regional Express Operating System, which is a network of regional trains that operate at speeds up to 90 mph.