treasure valley road dust study: final report - ResearchGate

January, February, and March were used to account for the effects of precipitation on road dust
emissions.
Yearly average emissions were calculated by applying the summer emissions potentials
in Table 5-1 and Table 5-2 to all non-Winter (i.e. not January, February, or March) months. The
effect of precipitation for each non-winter month was weighted by the number of days in that
month. The average emissions per day for winter were multipliedby the number of days (90) and
added to the average emissions per non-winter day multiplied by the number of days (275). The
total was divided by 365 to arrive at an annual-average emissions inventory.
5.1.2 Future year paved road emissions
Emissions inventories for future years were calculated similarly to the year 2000. Traffic
Demand Model results for the years 2010, 2015, and 2020 were combined with emissions
potentials to obtain emissions factors on a link-by-link basis. Since no actual TRAKER data are
available for future years, the emissions potentials for future year inventories were exclusively
calculated by equation (5-2) and Table 5-1 and Table 5-2. Note that the road setting
(urban/rural) was re-evaluated for each link in the TDM for each year. The future year
populations for individual census tracts were calculated by summing the number of houses in
each Traffic Analysis Zone that is contained within the tract and scaling with year 2000
populations. This approach assumes that the number of people per household remains constant
between the year 2000 and all future years. A map delineating the urban/rural zones for each of
the TDM years modeled is shown in Figure 5-2. For precipitation corrections, the historical
average correction factors shown in Table 5-4 were used.
5.1.3 Episodic paved road emissions
In addition to the years, 2000, 2010, 2015, and 2020, daily emissions inventories were
also assembled for January 1-9, 1991 and December 20-26, 1999. For days without
precipitation, winter dry paved roads emissions were used. For days with precipitation, for each
0.25mm 30 minutes of zero emissions were assumed. The total number of hours of zero
emissions for a given day was calculated, subtracted from 24, and then divided by 24 to give a
precipitation modifier ratio. This ratio was then multiplied by the dry paved road emissions rate
to give the paved road emissions for that day.
5.1.3.1 December 20 –26, 1999
Because of the episode’s proximity to the beginning of the year 2000, year 2000 TDM results
were used to calculate daily dry paved road emissions rates.
5.1.3.2 January 1 – 9, 1991
For the January 1-9, 1991 episode, the dry paved emissions were estimated from the year
2000 Traffic Demand Model network. The total vehicle miles traveled (VMT) in 1991 were
estimated by regressing the year 2000, 2010, 2015, and 2020 Total VMTs (see Figure 5-3). The
VMT for 1991 (6.77 million miles) was then divided by the VMT for 2000 (8.79 million miles)
to arrive at a correction factor for 1991 dry paved emissions. Based on this analysis, 1991 dry
paved emissions were 77.1% of 2000 dry paved emissions.
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