treasure valley road dust study: final report - ResearchGate

5.1.1.1a
Roads covered by Traffic Demand Model
The Traffic Demand Model (TDM) network of roads provided by COMPASS includes a
physical link for each direction of travel of each major roadway. Major roadways include
“Locals”, “Collectors”, “Minor Arterials”, “Principal Arterials”, and “Interstates”. Minor streets
in residential neighborhoods are not physically represented in the TDM. Emissions potential
estimates for those types of roads is discussed in the next section.
For the year 2000 paved road inventory, direct TRAKER measurement results were used
whenever possible. That is, when the TRAKER was used to traverse a road that corresponds to a
link in the Traffic Demand Model network, the TRAKER measurement obtained on that road
was used to represent the emissions potential for that link. For the remainder of the roads in the
TDM, the empirical relationship expressed in equation (5-2) was used to estimate the emissions
potential. Table 5-1 summarizes the empirical values used for C C,S,T and x. The travel speed
associated with each link is reported as part of the TDM network representation.
Table 5-1. Emissions potentials for roads that are physically represented in the TDM by season, county, and
setting
Season County Setting a [g/vkt/mps] x
C C,S,T
S Ada Rural 47 -1.47
S Ada Urban 45 -1.39
S Canyon Rural 370 -2.05
S Canyon Urban 462 -2.03
W Ada Rural 43 -1.32
W Ada Urban 72 -1.38
W Canyon Rural 12 -1.05
W Canyon Urban 318 -1.86
a The setting of a road is designated based on census tract data. If a road falls into a census tract where the ratio of
population to area is greater than 385 people per square kilometer, then the road setting is considered urban;
otherwise, it is rural.
5.1.1.1b
Residential Roads
Residential roads are not present in the TDM as physical entities. Instead, they are
represented by a series of centroid connectors (Figure 5-1). In practice, this means that a small
neighborhood is represented by a point, referred to as a traffic analysis zone (TAZ), and is
connected to major roadways in the TDM (non-residentials) by centroid connectors. This
modeling tool does not allow for direct overlay of TRAKER measurements obtained on
residentials roads. Therefore, an empirical relationship between emissions potential and road
speed was not possible to obtain for residential roads. The emissions potentials for residential
roads are summarized in Table 5-2 and are independent of speed (i.e. x=0).
5.1.1.2 Emissions for dry paved roads
The calculation of dry paved road emissions of PM 10 is straightforward once the
emissions potentials have been calculated for the individual links in the TDM. The dry PM 10
emissions for a link are simply:
E ?
i, 10
? EFi
, 10?
Li
Vi
Eq (5-3)
5-2