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Class-8 Heavy Truck Duty Cycle Project Final Report - Center for ...

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analysis controlling <strong>for</strong> the type of terrain showed that fuel efficiencies are, as expected, greatly<br />

affected by the type of terrain. Table 25 shows the results of this analysis in which the fuel<br />

efficiencies were computed <strong>for</strong> different types of terrains using the in<strong>for</strong>mation provided by the<br />

databus. Notice that in the case of sever downslopes (i.e., grades that are < -4%) the fuel efficiencies<br />

observed are significantly higher than <strong>for</strong> other types of terrains. Nevertheless, this issue needs to be<br />

studied further by per<strong>for</strong>ming a similar analysis as the one presented here (i.e., taking into account the<br />

speed of the vehicle), but controlling <strong>for</strong> the type of terrain to isolate its effect on achieved fuel<br />

efficiency.<br />

Table 25. Fuel Economy <strong>for</strong> <strong>Class</strong>-8 <strong>Truck</strong>s as a Function of Type of Terrain and Type of Tractor Tires<br />

Type of Terrain<br />

%<br />

Total<br />

Obs.<br />

All<br />

<strong>Truck</strong>s<br />

Average Fuel Efficiency (mpg)<br />

Tractors<br />

with<br />

Duals<br />

Tractors<br />

with<br />

NGSWBTs<br />

% Diff<br />

NGSWBTs<br />

vs. Duals<br />

Severe Upslope (>4%) 0.7% 2.90 2.86 2.94 2.91%<br />

Mild Upslope (1% to 4%) 13.2% 4.35 4.25 4.44 4.35%<br />

Flat Terrain (1% to 1%) 72.4% 7.33 7.08 7.58 7.13%<br />

Mild Downslope (-4% to -1%) 12.6% 15.11 14.64 15.57 6.36%<br />

Severe Downslope (

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