Estimating the Effects of Pavement Condition on Vehicle Operating Costs (2012) / Chapter Skim
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8The most recent VOC model found in the literature review is the HDM 4. It incorporates a mechanistic–empirical model of fuel consumption.
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9 Name Description Unit Total power (Ptot) for 0, uphill/level for 0, downhill tr tot accs eng tr tot tr accs eng tr P P P P P edt P edtP P P P = + + ≥ = + + < kW edt Drive-train efficiency factor factor Engine and accessories power (Pengaccs = Peng + accsP )
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10 Name Description Unit Aerodynamic forces (Fa)
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11 Vehicle Type Effect Mass Ratio Model Coefficients a0 a1 a2 Motorcycle 1.1 0 0 Small car 1.14 1.01 399 Medium car 1.05 0.213 1260.7 Large car 1.05 0.213 1260.7 Light delivery car 1.1 0.891 244.2 Light goods vehicle 1.1 0.891 244.2 Four-wheel drive 1.1 0.891 244.2 Light truck 1.04 0.83 12.4 Medium truck 1.04 0.83 12.4 Heavy truck 1.07 1.91 10.1 Articulated truck 1.07 1.91 10.1 Mini bus 1.1 0.891 244.2 Light bus 1.1 0.891 244.2 Medium bus 1.04 0.83 12.4 Heavy bus 1.04 0.83 12.4 Coach 1.04 0.83 12.4 Source: Bennett and Greenwood (2003b) Table 3-6.
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12 Table 3-10 summarizes the results of the paired t-test that was conducted. A paired samples t-test failed to reveal a statistically reliable difference between the mean fuel consumption measured using Graphtec (mean = 102.38 mL/km, standard deviation = 13.09 mL/km)
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13 Variables Winter Summer 11/24/2008 11/25/2008 06/05/2009 06/06/2009 06/07/2009 Ambient temperature (°C) 0–2 1–3 28.9–29.2 27.2–28.3 22.5–25.2 Wind speed (m/s)
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14 vehicles used in field trials. Tests for trucks were conducted using loaded (Figure 3-3)
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15 Each vehicle had a data logger (scanner) connected to the OBD connector and the vehicle was driven at different speeds on cruise control to reduce the acceleration and deceleration cycles.
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16 (a) Calibration Procedure for Medium Car (b)
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17 (g) Calibration Procedure for Light Truck (h)
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18 • Kcr2, which modifies the tractive power; • KPea, which modifies the accessories and engine power. The calibration procedure determines the coefficients required to minimize the sum of squared errors (i.e., sum of squared differences between the observed field values and those predicted using HDM 4 model)
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19 ments without cruise control for the heavier vehicles. The HDM 4 overpredicts fuel consumption in the high range (above 200 mL/km)
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20 (a) Medium Car (b)
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21 for scientific research. Lower confidence levels would lead to perhaps too many variables that are statistically significant and greater confidence would require more data to generate intervals of usable lengths.
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22 The sensitivity analyses for the current and calibrated models (Figures 3-9a and 3-9b, respectively)
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23 Source: adapted from Michelin (2003)
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Speed Vehicle Class Calibrated HDM 4 model Current HDM 4 model Base (mL/km) Adjustment factors from the base value Base (mL/km)
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( ) Name Description Unit Aerodynamic forces (Fa)
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26 Vehicle Class Number of Axles CD AF (m2) NW M (tons)
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