Shadow tolls are payments made by government to the private sector operator (concessionaire) of a road. The payments are based on the number and type (classification) of vehicles using the road. The main advantage of this system is that it eliminates the need for drivers to pay tolls directly and the associated toll collection costs.
A traffic counter classifier is used to measure the traffic volume by classification. The traffic counter connects to an inroad sensor array including loops and piezoelectric axle detection sensors.

The TDC Systems HI-TRAC® AVC Shadow Tolling System is a traffic data collection system intended for multi-lane Automatic Vehicle Counter/Classifying (AVC) mounted in a roadside cabinet at a permanent location.

The system provides a low cost means of recording vehicle classification data without interruption to traffic flow. The system can be used as a statistical data gathering device to record the pattern of highway traffic as well as a means of event monitoring and incident detection.

The HI-TRAC AVC supports all combinations of inroad sensors as required to meet vehicle classification accuracy including:

• Loop-Loop
• Loop-Piezo-Loop
• Piezo-Loop-Piezo
• Loop-Piezo-Loop-Piezo

The HI-TRAC® AVC may be powered from a 12V DC supply. Power Consumption is less than 1 Watt and the system can work autonomously from solar panel and associated battery & charge regulator.

Modem and landline or GSM/GPRS communications options are available. A small, vandal proof GSM antenna is available for installation on the top of the roadside cabinet.