treasure valley road dust study: final report - ResearchGate

Table 4-3. TRAKER street survey coverages by season, county, and road class.
County
Road Class
kilometers
covered with
TRAKER
County
Road Class
kilometers
covered with
TRAKER
Ada Collector 62.0 Ada Collector 65.8
Ada Interstate 41.1 Ada Interstate 47.8
Ada Local/Residential 44.6 Ada Local/Residential 46.3
Ada Minor Arterial 60.9 Ada Minor Arterial 75.7
Ada Principal Arterial 51.9 Ada Principal Arterial 60.1
Ada Unpaved 14.9 Ada Unpaved 18.4
Ada All roads 275.4 Ada All roads 314.0
Canyon Collector 9.5 Canyon Collector 8.5
Canyon Interstate 30.3 Canyon Interstate 33.4
Canyon Local/Residential 15.3 Canyon Local/Residential 11.3
Canyon Minor Arterial 56.4 Canyon Minor Arterial 43.0
Canyon Principal Arterial 39.9 Canyon Principal Arterial 23.8
Canyon Unpaved 0.0 Canyon Unpaved 0.0
Canyon All roads 151.5 Canyon All roads 120.1
Ada &
Canyon
Winter
All roads 426.9
Ada &
Canyon
Summer
All roads 434.1
4.2.1.1 Effect of Speed and VMT
The effect of vehicle speed and the volume of traffic per lane on road dust emissions
potentials were assessed for all non-residential roads. Residential roads were not included
because they are not physically represented in the Traffic Demand Model. Therefore, the
associated speeds and traffic volumes were also not available for residentials. It is important to
note that “speed” here refers to the speed attributed to the road in the Traffic Demand Model and
not the speed of the TRAKER vehicle itself. The dependence of the emissions potential on
speed and traffic volume was assumed to have the following form:
b
or equivalently,
? x ? y
? CC, S,
T
? s ? v
(4-7)
log( b)
? lCC , S , T
? x?
log( s)
? y?
log( v)
(4-8)
where b is the emissions potential in units of [g/vkt/mps], C C,S,T is a constant that is specific to
the county (Ada or Canyon), setting (urban or rural), and time of year (winter or summer), l C,S,T
is the base 10 logarithm of C C,S,T , s is the road speed, v is the number of vehicles per lane per
day, and x and y are positive empirical constants. The form of Eq (4-7) is appealing because as
speed and traffic volume increase, the road dust emissions potential decreases, a result that is
consistent with physical expectation.
The results of regressions of log(b) vs. log(s) and log(v) are shown in Table 4-4. Three
sets of linear regression results are shown in the Table: Log (b)vs. Log(s) and Log(v) shown as
option 1 in the table, Log(b) vs. Log(s) only shown as option 2 in the table (assumes emissions
potential independent of per lane traffic volume), and Log(b) vs. Log(v) only shown as option 3
in the table (assumes emissions potential independent of road speed). For each of the three
4-9