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Reply to Comments on the Proposed On-Road Vehicle and Engine Emission Regulations - Transportation Systems Branch

Appendix 1: Scenario Analysis: Fleet Average NOx Emissions in Canada - Estimation of Future Fleet Average NOx Emission Rates

The Canadian sales mix data and vehicle/bin distributions described previously can be used to estimate fleet average NOx emission rates for the 2009 model year, when the Tier 2 program will be fully implemented.

For the U.S. sales mix, the EPA2 assumed that the sales of light-duty trucks will increase to 60% of the light vehicle market in 2008 and then level off, but the distribution of sales across the four light-duty truck categories (i.e., LDT1 at 18%, LDT2 at 57%, LDT3 at 17% and LDT4 at 8%) is assumed to remain constant at 1999 levels. For the purposes of comparison, the Canadian distribution of sales across the four light-duty truck categories is also held constant at the Canadian 2000 levels (i.e., LDT1 at 8.7%, LDT2 at 62.3%, LDT3 at 18.3% and LDT4 at 10.7%)1. The overall percentage of light-duty trucks in the Canadian combined car and light-duty truck fleet, however, is varied according to the data presented previously. Table 5 presents the fleet average NOx emission rates calculated using the two vehicle/bin distributions and percentage of light-duty trucks in Canada at 40, 47, 55 and 60%.

Table 5: Estimated Fleet Average NOx Emission Rates
 U.S. Fleet AverageCanadian Fleet Average
 60% trucks40 % trucks (2000MY)47% trucks55% trucks60% trucks
LDV0.4000.5970.5310.4500.400
LDT10.1080.0350.0410.0480.052
LDT20.3420.2510.2920.3430.374
LDT30.1020.0740.0860.1010.110
LDT40.0480.0430.0500.0590.064
MOBILE6 Vehicle/Bin Distribution Overall Fleet Average:0.0700.0610.0660.0720.075
Alternative Distribution Overall Fleet Average:0.0700.0680.0700.0710.072

Using the vehicle/bin distribution assumed in the MOBILE6 model and the current percentage of light-duty trucks in the Canadian fleet (40%, derived from the 2000 Canadian registration and EPA certification data), the Canadian fleet average would be 0.061 g/mi, which is lower than the corresponding U.S. fleet average. Using Automotive News forecast, which predicts 47% trucks, the fleet average would be 0.066 g/mi. The trend observed in the Automotive News data (i.e., 5% less trucks in Canadian fleet compared to the U.S. fleet) yields 55% trucks in the Canadian fleet and the resultant fleet average would be 0.072 g/mi. In the extreme case that the Canadian light-duty truck population increases to 60%, the Canadian overall fleet average would be slightly higher than the U.S. at 0.075 g/mi.

Using the alternative distribution with the majority of vehicles certified to bin 5, all scenarios indicate a fleet average in Canada between 0.068 and 0.072 g/mi.

The population of MDPVs is not included in the calculations for the Canadian or U.S. fleet averages since defining this class of vehicle separately will be new for the 2004 and later model years and there are no data currently available to quantify the MDPV population. MDPVs, while low in population, would likely be certified to a bin with high emission standards. The bin distribution selected by manufacturers would be adjusted accordingly to achieve a NOx emission rate of 0.07 g/mi in the U.S.


1 Trends show that when Canadian consumers replace their traditional passenger cars with light-duty trucks, they tend to purchase lighter trucks (i.e., LDT1 or LDT2). Holding the 2000 model year percentages of LDT1-4 categories constant while varying the overall percentage of truck sales may not reflect this trend. It does, however, provide a conservative method to estimate the fleet average NOxemission rate and is consistent with the approach used in the U.S. EPA reference.

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