An operator independent Toll Audit system is provided at toll plazas by comparing traffic volumes and classification at a toll plaza to autonomous classifiers downstream from a facility. In order to verify the performance of reference classifier, two RAKTEL axle classifiers operate in tandem with each other normally 30m apart. The tracking of these two classifiers ensure that a high degree of confidence can be attached to the integrity of the recorded data.

This system is currently a requirement of the South African National Roads Agency at all their plazas.