Blended Aftertreatment Systems

By Clean Train Propulsion & Engine, Fuel and Emissions Engineering

The patented Blended Aftertreatment System (BATS) is a unique concept developed by RPS that allows EMD locomotives fitted with HEP generators to meet current emissions requirements without replacing the proven and reliable 645 and 710 main engine. The key to the concept is combining the HEP Exhaust with the main exhaust in order to facilitate mixing and delivery of the dosing agent (Urea) to optimize the emissions reduction for both engines. The system consists of Compact Selective Catalytic Reduction (CSCR) with a Urea storage and injection circuit, respective exhaust ducting, and a system controller that monitors and dispenses the Urea as a function of system load.


The BATS Tier 4X is the latest iteration of the product.  Built on the proven and EPA Certified Blended After Treatment  (BATS) Architecture, the  “X” signifies EXTRA as the upgrade will allow legacy dual engine passenger locomotives to provide:

  • Tier 4 emissions with added power electronics package
  • Tier 5 emissions when stationary providing hotel power
  • Limp home capability
  • 600 HP of Boost Tractive Power over current F59 locomotives
  • Higher average fuel efficiency than new locomotives

The BATS is an improvement to the EF&EE ‘Compact SCR’ system previously tested in service with Metrolink in 2010.

SCAX 865 Compact SCR

The Selective Catalytic Reduction (SCR) unit in the BATS is based on the original Compact SCR that underwent  over a year of combined testing and commuter rail service as part of a demonstration effort for Metrolink performed in 2010. The lessons learned from this effort were incorporated into the first BATS system that was operated in service on North Carolina Transportation Department’s (NCDOT) Locomotive 1859 in 2016 and 2017.  Fitted with the BATS, NCDOT’s 1859 became the first passenger locomotive in the United States to achieve Tier 4 NOx Emissions levels in passenger service resulting in the BATS receiving EPA Certification in 2018.  

The Path to Near Zero Emissions Commuter Rail

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