The test is performed in accordance with European Directive 70/220/EEC – Annex III and is based upon statistical evaluation of a minimum of 4 test runs.
The test results are considered to be valid when the statistical accuracy of the average test values is ≤ 2%.
The test can be performed at any speed according to the manufacturer’s requirements, but must follow the general procedure below:
- Accelerate the vehicle to a speed 10 km/h greater than the test start speed (user definable – 125 km/h in the diagram)
- Place gearbox in neutral
- Measure the time taken for the vehicle to decelerate from the start speed to the stop speed (user definable – 85 km/h in the diagram). This is time t1.
- Repeat steps 1-3, but in the opposite direction. This is time t2
- Take the average time of these two test runs (t1 + t2)/2. This is the time T
Repeat steps 1 to 5 until such time that the statistical accuracy of the average is not more than 2%
The statistical accuracy (p) is defined by:
Where:
n = Number of tests
s = standard deviation
| n | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | |
| t | 3.2 | 2.8 | 2.6 | 2.5 | 2.4 | 2.3 | 2.2 | 2.2 | 2.2 | 2.2 | 2.2 | 2.2 |
| 1.6 | 1.25 | 1.06 | 0.94 | 0.85 | 0.77 | 0.73 | 0.66 | 0.64 | 0.61 | 0.59 | 0.57 | |