The term 'ACELA RUNNER' refers to an employee of AMTRAK, the national passenger rail service in the United States. An ACELA RUNNER is responsible for operating the Acela Express, which is AMTRAK's high-speed train service that runs along the Northeast Corridor between Washington, D.C. and Boston. The job requires a high level of skill and attention to detail, as the Acela Express is capable of reaching speeds of up to 150 miles per hour.