Velocity noise caused by poorly positioned antennas or by multipath reflections from nearby trees and buildings, can affect the measured time of an acceleration run or a deceleration run from a speed to zero.
For example, on an acceleration run, if the velocity channel is noisy, it is possible that a spike of velocity noise may go over the 100 km/h threshold earlier than the vehicle actually went over 100 km/h, hence producing a shorter time. It is good practice to run the VBOX in a lower dynamic mode for acceleration testing for this reason.
However, because distance is calculated by integration over time, this is effectively smoothing the data. This means that braking distances are much more tolerant of velocity noise. For a braking test, the VBOX should be in a high dynamic mode.