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40 CFR § 1037.527 - Aerodynamic measurements for vocational vehicles. 

---
identifier: "/us/cfr/t40/s1037.527"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 1037.527 - Aerodynamic measurements for vocational vehicles."
title_number: 40
title_name: "Protection of Environment"
section_number: "1037.527"
section_name: "Aerodynamic measurements for vocational vehicles."
chapter_name: "ENVIRONMENTAL PROTECTION AGENCY"
subchapter_number: "U"
subchapter_name: "AIR POLLUTION CONTROLS"
part_number: "1037"
part_name: "CONTROL OF EMISSIONS FROM NEW HEAVY-DUTY MOTOR VEHICLES"
positive_law: false
currency: "2026-03-24"
last_updated: "2026-03-24"
format_version: "1.1.0"
generator: "[email protected]"
authority: "42 U.S.C. 7401—7671q."
regulatory_source: "81 FR 74048, Oct. 25, 2016, unless otherwise noted."
cfr_part: "1037"
---

# 1037.527 Aerodynamic measurements for vocational vehicles.

This section describes an optional methodology for determining improved aerodynamic drag area, *C*<sub>d</sub>*A*, 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 *D**C*<sub>d</sub>*A* value relative to a baseline vehicle. Determine a *D*<sub>d</sub>*A* 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 *C*<sub>d</sub>*A* value for a vehicle representing a production configuration without the aerodynamic improvement. Repeat this testing and measure *C*<sub>d</sub>*A* 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 *C*<sub>d</sub>*A* in m
<sup>2</sup> to two decimal places. Calculate *D*<sub>d</sub>*A* by subtracting the drag area for the test vehicle from the drag area for the baseline vehicle.

[89 FR 29783, Apr. 22, 2024]