As of 2026, the standard crew size for a major freight or passenger train in the United States is two people: a locomotive engineer and a conductor. This was codified in a 2024 federal safety rule mandated by the Department of Transportation, requiring a second crewmember on board most trains to enhance safety and emergency response protocols. While technology has advanced to allow for "Positive Train Control" and some automated systems, the two-person crew remains the legal and practical gold standard to manage mechanical issues, monitor long consists (some over 3 miles long), and handle communications. In some specialized contexts, such as light-rail transit or short-haul industrial lines, "Single Person Train Operation" (SPTO) is utilized, but for the vast majority of the heavy rail network, a team of two is required to ensure the train moves safely through diverse terrain and weather conditions.