Ball-Bank Method

The steps for determining the advisory speed using a ball-bank indicator will remain in this section until the compliance date of January 1, 2013 has passed.
The speed to be posted will be based on results obtained from test runs in a vehicle equipped with either a mechanical ball-bank indicator (see Figure 5-7) or an electronic accelerometer, not the calculated value. (See following discussion of “Calculated Speed.”)
Two types of ball-bank indicators. (click in image to see full-size image)
Figure 5-7. Two types of ball-bank indicators.