Author Contributions
Conceptualization, B.F., C.A., D.L.M., J.R.C., M.B., R.B., R.T.F. and S.A.G.; methodology, B.F., C.A., D.L.M., E.T.C., J.R.C., M.B., R.B., R.T.F., S.A.G., S.H. and T.M.B.; software, B.F., C.A., D.L.M., R.B. and S.A.G.; validation, B.F., C.A., D.L.M., E.T.C., R.B., S.A.G., S.H. and T.M.B.; formal analysis, B.F., C.A., D.L.M., E.T.C., R.B., S.A.G., S.H. and T.M.B.; investigation, B.F., C.A., D.L.M., E.T.C., R.B., S.A.G., S.H. and T.M.B.; resources, B.F., C.A., D.L.M., R.B. and S.A.G.; data curation, B.F., C.A., D.L.M., J.R.C., M.B., R.B., R.T.F. and S.A.G.; writing—original draft preparation, B.F., C.A., D.L.M., E.T.C., R.B., S.A.G., S.H. and T.M.B.; writing—review and editing, B.F., C.A., D.L.M., E.T.C., J.R.C., M.B., R.B., R.T.F., S.A.G., S.H. and T.M.B.; visualization, D.L.M.; supervision, B.F., C.A., D.L.M., E.T.C., R.B., S.A.G., S.H. and T.M.B.; project administration, B.F., C.A., R.B. and S.A.G.; funding acquisition, B.F., C.A., D.L.M., R.B. and S.A.G. All authors have read and agreed to the published version of the manuscript.
Figure 1.
Salt Lake City and Salt Lake County within Utah and the United States (left inset) with the interstate highways (I-15, I-80, I-215) noted.
Figure 1.
Salt Lake City and Salt Lake County within Utah and the United States (left inset) with the interstate highways (I-15, I-80, I-215) noted.
Figure 2.
Study area showing the instrument locations at (a) Willow Springs Elementary and (b) Bonneville Elementary. The parking location of the van is denoted by a yellow star, the playground site is marked by a red circle, and the approximate location of the indoor site is marked by a blue sign. Images courtesy of Google Maps.
Figure 2.
Study area showing the instrument locations at (a) Willow Springs Elementary and (b) Bonneville Elementary. The parking location of the van is denoted by a yellow star, the playground site is marked by a red circle, and the approximate location of the indoor site is marked by a blue sign. Images courtesy of Google Maps.
Figure 3.
Time series (tick mark denotes midnight) for Willow Springs campaign (10–17 January 2020) for (a) carbon dioxide, (b) methane, (c) nitrogen oxides, (d) fine particulate matter, and (e) ozone.
Figure 3.
Time series (tick mark denotes midnight) for Willow Springs campaign (10–17 January 2020) for (a) carbon dioxide, (b) methane, (c) nitrogen oxides, (d) fine particulate matter, and (e) ozone.
Figure 4.
Van pollutant readings comparisons for Willow Springs campaign (10–17 January 2020) for (a) carbon dioxide vs. methane, (b) carbon dioxide vs. nitrogen oxides, (c) carbon dioxide vs. fine particulate matter, and (d) nitrogen oxides vs. fine particulate matter.
Figure 4.
Van pollutant readings comparisons for Willow Springs campaign (10–17 January 2020) for (a) carbon dioxide vs. methane, (b) carbon dioxide vs. nitrogen oxides, (c) carbon dioxide vs. fine particulate matter, and (d) nitrogen oxides vs. fine particulate matter.
Figure 5.
Site pollutant readings comparisons for Willow Springs campaign (10–28 January 2020) for fine particulate matter.
Figure 5.
Site pollutant readings comparisons for Willow Springs campaign (10–28 January 2020) for fine particulate matter.
Figure 6.
Time series (tick mark denotes midnight) for Bonneville Phase 1 campaign (13–27 September 2019) for (a) carbon dioxide, (b) methane, (c) nitrogen oxides, (d) fine particulate matter, and (e) ozone.
Figure 6.
Time series (tick mark denotes midnight) for Bonneville Phase 1 campaign (13–27 September 2019) for (a) carbon dioxide, (b) methane, (c) nitrogen oxides, (d) fine particulate matter, and (e) ozone.
Figure 7.
Van pollutant readings comparisons for Bonneville Phase 1 campaign (13–27 September 2019) for (a) carbon dioxide vs. methane, (b) carbon dioxide vs. nitrogen oxides, (c) carbon dioxide vs. fine particulate matter, and (d) nitrogen oxides vs. fine particulate matter.
Figure 7.
Van pollutant readings comparisons for Bonneville Phase 1 campaign (13–27 September 2019) for (a) carbon dioxide vs. methane, (b) carbon dioxide vs. nitrogen oxides, (c) carbon dioxide vs. fine particulate matter, and (d) nitrogen oxides vs. fine particulate matter.
Figure 8.
Site pollutant readings comparisons for Bonneville Phase 1 campaign (13–27 September 2019) for (a) fine particulate matter and (b) ozone.
Figure 8.
Site pollutant readings comparisons for Bonneville Phase 1 campaign (13–27 September 2019) for (a) fine particulate matter and (b) ozone.
Figure 9.
Time series (tick mark denotes midnight) for Bonneville Phase 2 campaign (13–27 February 2020) for (a) carbon dioxide, (b) methane, (c) nitrogen oxides, (d) fine particulate matter, and (e) ozone.
Figure 9.
Time series (tick mark denotes midnight) for Bonneville Phase 2 campaign (13–27 February 2020) for (a) carbon dioxide, (b) methane, (c) nitrogen oxides, (d) fine particulate matter, and (e) ozone.
Figure 10.
Van pollutant readings Bonneville Phase 2 campaign (13–27 February 2020) for (a) carbon dioxide vs. methane, (b) carbon dioxide vs. nitrogen oxides, (c) carbon dioxide vs. fine particulate matter, and (d) nitrogen oxides vs. fine particulate matter.
Figure 10.
Van pollutant readings Bonneville Phase 2 campaign (13–27 February 2020) for (a) carbon dioxide vs. methane, (b) carbon dioxide vs. nitrogen oxides, (c) carbon dioxide vs. fine particulate matter, and (d) nitrogen oxides vs. fine particulate matter.
Figure 11.
Site pollutant readings comparisons for Bonneville Phase 2 campaign (13–27 February 2020) for (a) fine particulate matter and (b) ozone.
Figure 11.
Site pollutant readings comparisons for Bonneville Phase 2 campaign (13–27 February 2020) for (a) fine particulate matter and (b) ozone.
Figure 12.
Weekday time of day pre- and post-campaign: (a) total vehicle counts, (b) idling vehicle counts, and (c) total vehicle idling time.
Figure 12.
Weekday time of day pre- and post-campaign: (a) total vehicle counts, (b) idling vehicle counts, and (c) total vehicle idling time.
Table 1.
Campaign timelines including sensor availability.
Table 1.
Campaign timelines including sensor availability.
Site | Pollutant | Willow Springs | Bonneville Phase 1 | Bonneville Phase 2 |
---|
Van | CH4, CO2, NOx, PM2.5, O3 | 10–17 January 2020 | 16–20 September 2019 | 14–21 February 2020 |
Playground | PM2.5 | - | 13–27 September 2019 | 13–26 February 2020 |
O3 | - | 13–27 September 2019 | 14–26 February 2020 |
School (Indoor) | PM2.5 | 15–28 January 2020 | - | - |
O3 | - | 16–27 September 2019 | 21–26 February 2020 |
Table 2.
Hourly mean and range (minimum–maximum) pollutant readings for each campaign.
Table 2.
Hourly mean and range (minimum–maximum) pollutant readings for each campaign.
Site | Pollutant | Willow Springs | Bonneville Phase 1 | Bonneville Phase 2 |
---|
Van | CH4 (ppm) | 1.95 (1.90–2.26) | 1.91 (1.86–2.07) | 2.01 (1.92–2.38) |
CO2 (ppm) | 430.29 (411.97–558.54) | 414.78 (402.51–463.62) | 439.33 (417.88–525.75) |
NOx (ppb) | 7.81 (0.00–68.11) | 4.54 (0.00–23.00) | 5.46 (0.00–32.53) |
PM2.5 (µg/m3) | 1.43 (0.02–6.62) | 2.08 (0.42–5.56) | 3.21 (0.30–10.50) |
O3 (ppb) | 32.32 (27.89–54.36) | 70.60 (36.93–82.95) | 61.71 (32.78–79.00) |
Playground | PM2.5 (µg/m3) | - | 1.75 (0.20–7.68) | 1.46 (0.02–7.23) |
O3 (ppb) | - | 38.11 (2.32–69.16) | 28.15 (0.00–52.2) |
School (Indoor) | PM2.5 (µg/m3) | 2.72 (0.08–12.60) | - | - |
O3 (ppb) | - | 11.34 (2.28–31.03) | 15.32 (0.00–36.03) |
Table 3.
Willow Springs campaign Spearman correlation test results for van pollutant readings.
Table 3.
Willow Springs campaign Spearman correlation test results for van pollutant readings.
Equipment | ρ (rho) | 95% CI | p-Value |
---|
CO2 vs. CH4 | 0.851 | 0.793–0.909 | <2.2 × 10−16 |
CO2 vs. NOx | 0.925 | 0.894–0.957 | <2.2 × 10−16 |
CO2 vs. PM2.5 | 0.505 | 0.374–0.637 | <2.2 × 10−16 |
NOx vs. PM2.5 | 0.536 | 0.412–0.660 | 7.094 × 10−14 |
Table 4.
Willow Springs correlation test results for site pollutant readings.
Table 4.
Willow Springs correlation test results for site pollutant readings.
Equipment | ρ (rho) | 95% CI | p-Value |
---|
Indoor vs. Van PM2.5 | 0.512 | 0.281–0.741 | 8.242 × 10−5 |
Table 5.
Bonneville Phase 1 Spearman correlation test results for van pollutant readings.
Table 5.
Bonneville Phase 1 Spearman correlation test results for van pollutant readings.
Equipment | ρ (rho) | 95% CI | p-Value |
---|
CO2 vs. CH4 | 0.550 | 0.393–0.707 | 2.743 × 10−9 |
CO2 vs. NOx | 0.332 | 0.126–0.537 | 0.002 |
CO2 vs. PM2.5 | 0.219 | 0.028–0.410 | 0.026 |
NOx vs. PM2.5 | 0.301 | 0.065–0.536 | 0.005 |
Table 6.
Bonneville Phase 1 Spearman correlation test results for site pollutant readings.
Table 6.
Bonneville Phase 1 Spearman correlation test results for site pollutant readings.
Equipment | ρ (rho) | 95% CI | p-Value |
---|
Playground vs. Van PM2.5 | 0.852 | 0.781–0.922 | <2.2 × 10−16 |
Playground vs. Van Ozone | 0.979 | 0.970–0.988 | <2.2 × 10−16 |
Indoor vs. Van Ozone | 0.428 | 0.240–0.615 | 6.633 × 10−6 |
Indoor vs. Playground Ozone | 0.493 | 0.402–0.584 | <2.2 × 10−16 |
Table 7.
Bonneville Phase 2 Spearman correlation test results for van pollutant readings.
Table 7.
Bonneville Phase 2 Spearman correlation test results for van pollutant readings.
Equipment | ρ (rho) | 95% CI | p-Value |
---|
CO2 vs. CH4 | 0.846 | 0.792–0.899 | <2.2 × 10−16 |
CO2 vs. NOx | 0.684 | 0.602–0.766 | <2.2 × 10−16 |
CO2 vs. PM2.5 | 0.628 | 0.528–0.729 | <2.2 × 10−16 |
NOx vs. PM2.5 | 0.450 | 0.306–0.594 | 9.184 × 10−10 |
Table 8.
Bonneville Phase 2 Spearman correlation test results for site pollutant readings.
Table 8.
Bonneville Phase 2 Spearman correlation test results for site pollutant readings.
Equipment | ρ (rho) | 95% CI | p-Value |
---|
Playground vs. Van PM2.5 | 0.637 | 0.539–0.735 | <2.2 × 10−16 |
Playground vs. Van Ozone | 0.986 | 0.980–0.992 | <2.2 × 10−16 |
Indoor vs. Playground Ozone | 0.606 | 0.475–0.737 | 2.749 × 10−13 |
Table 9.
Bonneville Elementary Idle-Free Campaign vehicle counts and idling time.
Table 9.
Bonneville Elementary Idle-Free Campaign vehicle counts and idling time.
Day of Week | Pre-Campaign | Post-Campaign |
---|
Total Vehicles | Vehicles Idling | Idling Time (s) | Total Vehicles | Vehicles Idling | Idling Time (s) |
---|
Tuesday | Morning | 74 | 60 | 3755 | 63 | 41 | 2195 |
Afternoon | 39 | 19 | 2701 | 65 | 25 | 2166 |
Wednesday | Morning | 70 | 34 | 4438 | 75 | 43 | 1738 |
Afternoon | 45 | 15 | 1409 | 43 | 14 | 3027 |
Thursday | Morning | 74 | 51 | 4379 | 39 | 15 | 883 |
Afternoon | 17 | 8 | 1058 | 21 | 12 | 956 |
Friday | Morning | 99 | 58 | 5193 | 98 | 40 | 2279 |
Afternoon | 23 | 2 | 1152 | 29 | 6 | 1480 |
Table 10.
Bonneville Elementary Idle-Free Campaign aggregated and average values.
Table 10.
Bonneville Elementary Idle-Free Campaign aggregated and average values.
Time Period | Total Vehicles | Total Idling | Total Idle (s) | Idling (%) | Idling (s/veh) | Idling (s/idler) |
---|
Pre-Campaign | Morning | 317 | 203 | 17,765 | 64.04 | 56.04 | 87.51 |
Afternoon | 124 | 44 | 6320 | 35.48 | 50.97 | 143.64 |
Total | 441 | 247 | 24,085 | 56.01 | 54.61 | 97.51 |
Post-Campaign | Morning | 275 | 139 | 7095 | 50.55 | 25.80 | 51.04 |
Afternoon | 158 | 57 | 7629 | 36.08 | 48.28 | 133.84 |
Total | 433 | 196 | 14,724 | 45.27 | 34.00 | 75.12 |