TABLE 1.
Descriptive Statistics for Seattle and Tahoma High Capacity School Buses in the 2005−2006 School Year (>50 Seats)
|
Seattle |
Tahoma |
|||||
|---|---|---|---|---|---|---|
| All Buses | Subject Busesa | Monitored Busesb | All Buses | Subject Busesa | Monitored Busesb | |
| Number of Buses | 331 | 68 | 24 | 62 | 23 | 19 |
| DOC Usagec | 40.8% | 42.6% | 25.0% | 3.2% | 0% | 0% |
| OEM DOC | 24.8% | 26.5% | 25.0% | 3.2% | 0% | 0% |
| DPF Usage | 4.5% | 5.9% | 4.2% | 0% | 0% | 0% |
| ULSD Usage | 100% | 100% | 100% | 0% | 0% | 0% |
| Bus Mileage (in thousands) | 61 (57) | 60 (57) | 48 (43) | 110 (88) | 113 (87) | 117 (89) |
| Body Year | 2001 (5) | 2001 (4) | 2003 (4) | 1995 (7) | 1996 (6) | 1996 (6) |
| Seating Capacity | 70 (4) | 69 (3) | 70 (3) | 76 (5) | 77 (5) | 76 (5) |
| Engine Manufacturerd | ||||||
| International Truck | 54% | 53% | 46% | 48% | 52% | 53% |
| Cummins Inc. | 1% | 0% | 0% | 13% | 4% | 5% |
| Caterpillar | 34% | 34% | 50% | 39% | 43% | 42% |
| Front Engine | 98% | 100% | 100% | 42% | 30% | 37% |
| Opacity (%) | 7.1 (8.9) | 8.4 (10.8) | 4.6 (4.8) | 21.8 (19.1) | 17.5 (16.6) | 16.9 (16.5) |
| Frequent Service (<60 days) | 91% | 85% | 84% | 0% | 0% | 0% |
| Scheduled Maintenance Frequency (days) | 46 (4) | 47 (5) | 47 (5) | 132 (101) | 101 (32) | 101 (34) |
Continuous data are presented as the overall mean (SD).
a
Summarized values for subject buses represent the students' typical buses although substitute buses are occasionally used during periods of servicing or vehicle inspection.
b
Descriptive statistics presented for buses with valid data only.
c
25% and 27% of all Seattle buses and Seattle subject buses, respectively, were retrofit with aftermarket DOCs. All other DOCs were original equipment installed by the manufacturer.
d
Remaining buses have unknown engine types.