The NS GP33ECO is a 4-axle diesel-electric locomotive built by the Norfolk Southern Railway in its Juniata Locomotive Shop. The locomotive is a rebuild of the EMD GP50 designed to meet Tier 3 emissions standards. Norfolk Southern plans to convert a total of 25 GP50s. The first locomotive was completed in January 2015. The rebuild was funded in part by the federal Congestion Mitigation and Air Quality Improvement Program.