treasure valley road dust study: final report - ResearchGate

400
Ford Ranger on NS Road by DW1
400
TRAKER and HUMVEE on EW Road by DW1
350
EF = 20 s
R 2 = 0.65
350
Emissions Factor (g/vkt)
300
250
200
150
100
Emissions Factor (g/vkt)
300
250
200
150
100
EF = 24 s
R 2 = 0.68
50
50
0
0 2 4 6 8 10 12 14 16
Vehicle Speed (mps)
0
0 2 4 6 8 10 12 14 16
Vehicle Speed (mps)
400
350
Ford Ranger on NS Road by DW2
EF = 19 s
R 2 = 0.67
400
350
TRAKER and HUMVEE on EW Road by DW2
EF = 29.0 s
R 2 = 0.92
300
300
Emissions Factor (g/vkt)
250
200
150
Emissions Factor (g/vkt)
250
200
150
100
100
50
50
0
0 2 4 6 8 10 12 14 16
Vehicle Speed (mps)
0
0 2 4 6 8 10 12 14 16
Vehicle Speed (mps)
Figure 3-20. Unpaved road dust emissions factors versus vehicle speed for two weight classes of vehicles. The
Ford Ranger weighs ~1.5 Mg while the TRAKER and HUMVEE weigh ~3.5 to 4 Mg.
The reasonable curve fits shown in Figure 3-20 indicate that the relationship between emissions
factor and vehicle speed is approximately linear. This is consistent with the equation (See Eq 2-
1) used to model unpaved road dust emissions in the U.S. E.P.A.’s AP-42 documentation
(USEPA, 1995).
3.5 Comparison of TRAKER Measurements with Flux
By comparing the TRAKER signal (Eq. 1) with the emissions factors measured on the
down wind towers, a calibration for the TRAKER vehicle has been developed. This calibration
permits the inference of road dust emissions factors from valid TRAKER measurements.
Table 3-4 shows the average TRAKER signal measurements from the unpaved road tests.
The signal was calculated independently for both theright and left inlets. With the exception of
the 1.4 m/s pass on the East-West test section, signals from the left and right inlets agree with
each other within the limits of the measurement uncertainty. The TRAKER signal on the East -
West test section was typically more than one order of magnitude higher than on the more
heavily traveled North-South test section.
In section 3.3.4, tests on paved roads in two separate locations indicated that the
TRAKER signal increases approximately with the cube of the vehicle speed. In section 3.4, both
our measurements and those used to develop the AP-42 emissions factors indicated that unpaved
road emissions factors increase linearly with speed. Based on these two relationships, the
emissions factor should be approximately proportional to the TRAKER signal raised to the 1/3
power. That is:
3-22