A specific wheel arrangement under the UIC classification system used for heavy diesel-electric locomotives. It designates two trucks, each having one unpowered leading axle followed by three powered axles driven by individual traction motors. This design distributes the massive weight of early diesel units over more wheels to reduce axle load on the track.
Heard on the job
The old passenger units used a 1Co-Co1 arrangement to keep track speeds high without pounding the rail into dust.