Our analyses generally do not combine PM generated from engine combustion with that from tirewear and brakewear because they have different properties. However, if you need to combine tirewear, brakewear and exhaust PM, it is appropriate to divide the mass of the sum of all of the PM emissions (grams) from all of the processes (including brake wear and tire wear) by the vehicle miles traveled (VMT) reported for the running emission process to generate rates of grams per mile.
Why is it that when the brakewear and tirewear components of PM are written out using the "Inventory" calculation method, there is no associated VMT/activity data written to the "movesactivityoutput" table along with it for the SCCs pertaining to brakewea
Both brake wear and tire wear are based on the same vehicle activity data that is used to calculate running emissions. Repeating the VMT used (for each process) in the database would be redundant and could lead to errors when computing total VMT.
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