The year 2015 will be a landmark year in locomotive technology in the United States. Effective January 1st of that year, newly-manufactured U.S. line-haul and switch service (freight-and-passenger) locomotives must be manufactured to meet the fifth level of U.S. Environmental Protection Agency (EPA) emissions regulations since 2000. Achieving those emission levels will require aftertreatment technology in some form. Also effective December 31st of that year, U.S. railroads will be required to have in operation (on much of the rail network)1 a federally-mandated Positive Train Control (PTC) technology for collision avoidance. Class I U.S. freight railroads2 by the end of 2015 will have invested an estimated $5.8 billion in PTC technology, with a major emphasis on interoperability of PTC-equipped locomotives between different railroads. An estimated 17,000 locomotives will be retrofitted or equipped with PTC by the end of 2015 and most if not all newly-manufactured locomotives will be PTC equipped after 2015. For perspective, the U.S. freight railroad investment in PTC is roughly what the Class I railroads have spent the past 4–5 years combined on capital expenditures related to infrastructure expansion. This convergence of two new complex locomotive technologies in 2015 will create a large challenge, especially in locomotive maintainability, for freight railroads. Locomotive builders and aftertreatment suppliers must work together to provide Tier 4 locomotives with minimal impact on railroad operations. U.S. diesel locomotives share a common internal combustion engine technology with most Class 8 over-the-road diesel trucks, but the railroad and locomotive environment is very different from the highway truck environment, and a “cookie cutter” approach to replicating diesel truck aftertreatment on locomotives should be avoided. New EPA Tier 4 diesel locomotives should not be viewed as “Tier 2 or Tier 3 locomotives with truck-type exhaust aftertreatment added”. Baseline reliability of current locomotive designs must also be improved to compensate for the added complexities of both exhaust aftertreatment and PTC. This paper is focused toward educating (1) aftertreatment technology manufacturers and system integrators and (2) locomotive design engineers. The emphasis is on assisting them in understanding the operating and maintenance expectations for Tier 4 aftertreatment-equipped line-haul locomotives, from the perspective of a major freight railroad.

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