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COLD TEMPERATURE MOTOR VEHICLE EMISSIONS TESTING IN ALASKA
Impact/Purpose:
Develop credible CO idle emission factors for SIP emission inventories in Anchorage and Fairbanks and provide evidence for use of needed control measures such as engine block heaters
Description:
A motor vehicle emissions testing study was conducted in Anchorage and Fairbanks during the winter of 1998-99 to collect actual measurements of initial idle emission rates. The study was performed for a sample of 111 automobiles and light-duty trucks under cold wintertime ambient conditions and measured minute-by-minute idle emissions as vehicles warmed up from a cold start (without being plugged-in to a pre-heater). For a subset of the same vehicles, "plug-in" idle tests were also conducted under which vehicles were plugged-in prior to the cold start. Analysis of the data from the 1998-99 idle study produced the following findings: 1. Initial idle emission rates are significant under cold start conditions; 2. Idle emission benefits from fleet turnover are overstated in MOBILE5b (EPA's currently approved emissions model) and the MOBILE Cold CO model (Alternative MOBILE5b emissions model developed for Alaska)(based on a comparison of measured idle emissions by model year range to those predicted by MOBILE5b and Cold CO); and 3. Use of plug-in pre-heaters during long soaks over four hours provides substantial initial idle CO emission reductions (over 70%) compared to cold start idling without prior plug-in. In addition, to better understand the relationship between idle and trip-related emissions, FNSB, MOA, and ADEC funded a follow-on study to develop a representative drive cycle for wintertime operating conditions in Alaska and used it to collect modal data for a representative sample of vehicles. (Modal refers to emission test data collected on a second-by-second basis that can discern the effects of individual stop-and-go driving patterns or "modes" on emissions.) While the test results of that study are in draft form, the driving data collection effort showed that the combination of snow and ice on roadways in Fairbanks and Anchorage limits the amount of high speed and high acceleration rates compared to that observed in the lower 48 states. As a result, wintertime driving in Alaska is very similar to the drive cycle specified in the Federal Test Procedure (FTP). It also means that the high acceleration rates addressed in the Supplemental FTP (SFTP) do not occur in Alaska during the winter. As a result, the significant CO reductions anticipated to result from federal regulations that control emissions during off-cycle operation (e.g., hard accelerations) are not applicable during the winter in Alaska. This means that the CO reductions associated with the SFTP regulations employed in the Cold CO model should not be included in any emission inventory estimates prepared for Alaska.