---
kind: "section"
citation: "40 C.F.R. § 1066.401"
title: "40"
number: "1066.401"
heading: "Overview."
url: "https://uscodex.org/cfr/40/1066.401"
---

# §1066.401. Overview.

- (a) Use the procedures detailed in this subpart to measure vehicle emissions over a specified drive schedule. Different procedures may apply for criteria pollutants and greenhouse gas emissions as described in the standard-setting part. This subpart describes how to—
  - (1) **Determine road-load power, test weight, and inertia class.**
  - (2) **Prepare the vehicle, equipment, and measurement instruments for an emission test.**
  - (3) Perform pre-test procedures to verify proper operation of certain equipment and analyzers and to prepare them for testing.
  - (4) **Record pre-test data.**
  - (5) **Sample emissions.**
  - (6) **Record post-test data.**
  - (7) **Perform post-test procedures to verify proper operation of certain equipment and analyzers.**
  - (8) **Weigh PM samples.**
- (b) The overall test generally consists of prescribed sequences of fueling, parking, and driving at specified test conditions. An exhaust emission test generally consists of measuring emissions and other parameters while a vehicle follows the drive schedules specified in the standard-setting part. There are two general types of test cycles:
  - (1) **Transient cycles.** Transient test cycles are typically specified in the standard-setting part as a second-by-second sequence of vehicle speed commands. Operate a vehicle over a transient cycle such that the speed follows the target values. Proportionally sample emissions and other parameters and calculate emission rates as specified in subpart G of this part to calculate emissions. The standard-setting part may specify three types of transient testing based on the approach to starting the measurement, as follows:
    - (i) A cold-start transient cycle where you start to measure emissions just before starting an engine that has not been warmed up.
    - (ii) A hot-start transient cycle where you start to measure emissions just before starting a warmed-up engine.
    - (iii) A hot-running transient cycle where you start to measure emissions after an engine is started, warmed up, and running.
  - (2) **Cruise cycles.** Cruise test cycles are typically specified in the standard-setting part as a discrete operating point that has a single speed command.
    - (i) Start a cruise cycle as a hot-running test, where you start to measure emissions after the engine is started and warmed up and the vehicle is running at the target test speed.
    - (ii) Sample emissions and other parameters for the cruise cycle in the same manner as a transient cycle, with the exception that the reference speed value is constant. Record instantaneous and mean speed values over the cycle.

## Notes

### Authority

Authority: 42 U.S.C. 7401-7671q.

### Source

Source: 79 FR 23823, Apr. 28, 2014, unless otherwise noted.