The objective of this project was to quantify locomotive idle and start-up emissions, to answer the question: “At what point is it preferable from an emissions standpoint to idle a locomotive engine rather than shut down the engine and restart it when needed?” Idle and restart emissions tests were performed on two Tier 0 emission locomotives; a 1,120 kW EMD MP15-DC Switcher (UPY1378) and a 3,280 kW line-haul GE Dash9-44CW (BNSF4373). The results of the testing showed that continuous idling emissions of NOx and PM were greater than the start up emissions from the two test locomotives. The only exception was the 15-minute restart on the line haul locomotive BNSF4373, but this was envisioned to be due to a non-typical operational cycle of the GE AESS. The results of the extended idle tests showed that the older locomotive (UPY1378) operates at a relatively consistent idle emissions output through the four hours of extended idle. However, idle emissions from BNSF4373 varied over the idle period as the engine speed changes in response to on-board computer controls to accomplish engine warm-up and a series of other locomotive functions.

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