Section 1037.527 - Aerodynamic measurements for vocational vehiclesThis section describes an optional methodology for determining improved aerodynamic drag area, CdA, for vocational vehicles, as described in § 1037.520(m) , rather than using the assigned values. A vocational vehicle's aerodynamic performance is based on a [DELTA]CdA value relative to a baseline vehicle. Determine a [DELTA]dA value by performing A to B testing as follows:
(a) Use any of the procedures described in this subpart, with appropriate adjustments, for calculating drag area.(b) Determine a baseline CdA value for a vehicle representing a production configuration without the aerodynamic improvement. Repeat this testing and measure CdA for a vehicle with the improved aerodynamic design.(c) Use good engineering judgment to perform paired tests that accurately demonstrate the reduction in aerodynamic drag associated with the improved design.(d) Measure CdA in m2 to two decimal places. Calculate [DELTA]dA by subtracting the drag area for the test vehicle from the drag area for the baseline vehicle. 89 FR 29783 , Apr. 22, 2024