FTA Buy America requires that rolling stock purchased with federal transit funds be assembled in the US with a minimum domestic content percentage. Vehicles assembled in Mexico or Japan would not satisfy this requirement without a waiver, even if some components are US-sourced. Transit agencies must either procure domestically assembled vehicles, obtain an FTA waiver, or use non-federal funds for the foreign-built portion of a fleet order.

The key distinction is self-propulsion: vehicles under 860310 carry their own traction equipment and can move independently under electric power drawn from an external source. Non-self-propelled passenger cars — those that must be hauled by a separate locomotive — are classified under heading 8605. A trainset where power cars and trailer cars are permanently coupled as a unit is generally classified based on the essential character of the set, typically under the powered-vehicle heading.