Emission Testing Services

LOCOMOTIVE START-UP AND IDLING EMISSIONS

Client : South Coast Air Quality Management District

The SCAQMD has adopte regulations to limit idling by locomotive engines. In developing these rules, it received comments from the railroad industry that the increase in the number of start-ups due to idle restrictions could result in an emissions tradeoff. To clarify the relationship between start-up and idling emissions, the SCAQMD contracted with EF&EE to carry out emission measurements on two Metrolink locomotives, using the RAVEM system. Pollutants measured were particulate matter (PM), oxides of nitrogen (NOx), carbon dioxide (CO2), and total hydrocarbons (HC). CO concentrations were also measured, but the results were below detection levels. Quartz filters for elemental/organic carbon determinations were also collected for most of the tests.

The two locomotives tested were an EMD SD60 - a typical freight locomotive of the last generation - and an EMD F40 passenger locomotive. PM emissions at idle from the two locomotives tested were 0.66 and 0.38 grams per minute, respectively; and NOx emissions were 16.7 and 19.8 grams per minute. A significant fraction of the total PM (15% in the first case, and 49% in the second) is not emitted at the time, but retained in the exhaust system as "soup" - semivolatile hydrocarbons and lubricating oil - to be emitted subsequently when the locomotive returns to higher-load operation. The present Federal locomotive test procedure does not measure these substantially-increased PM emissions during the transient conditions following a period of idle.

The incremental emissions due to engine start-up from these locomotives were found to be small compared to the emissions produced under stabilized idle conditions. In none of the start-up tests conducted did these emissions exceed the equivalent of 8 minutes of idle operation. Based on these data, shutting down the engine and restarting it will result in reduced emissions compared to allowing it to idle, as long as the idle shutdown period is longer than eight minutes. The longer the shutdown period, the greater the emission benefits.