---
kind: "section"
citation: "40 C.F.R. § 1037.527"
title: "40"
number: "1037.527"
heading: "Aerodynamic measurements for vocational vehicles."
url: "https://uscodex.org/cfr/40/1037.527"
---

# §1037.527. Aerodynamic measurements for vocational vehicles.


This section describes an optional methodology for determining improved aerodynamic drag area, CdA, for vocational vehicles, as described in [§ 1037.520(m)](/cfr/40/1037.520.md?p=m), rather than using the assigned values. A vocational vehicle's aerodynamic performance is based on a DCdA value relative to a baseline vehicle. Determine a DdA 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 <I>C</I><I>d</I><I>A</I> in m 2 to two decimal places.** Calculate DdA by subtracting the drag area for the test vehicle from the drag area for the baseline vehicle.

## Notes

### Amendments

[89 FR 29783, Apr. 22, 2024]

### Authority

Authority: 42 U.S.C. 7401—7671q.

### Source

Source: 81 FR 74048, Oct. 25, 2016, unless otherwise noted.

### Amendments

[89 FR 29783, Apr. 22, 2024]