Automatic vehicle monitoring system

An apparatus for detecting the direction and the number of vehicles passing by a predetermined point along a vehicle path, said apparatus comprising:

• first and second magnetic sensors positioned in a spaced relationship, the first of said sensors being oriented for maximum sensitivity ot magnetic disturbance at a first point on said vehicle path and the second of said sensors being oriented for maximum sensitivity to magnetic disturbance at a second point on said vehicle path;
• first and second analog signal processing channels connected to receive output signals from first and second magnetic sensors, respectively, each of said channels including,
• differentiating means for providing a signal which is a derivative of the signal from the magnetic sensor, and
• a zero-crossing detector connected to receive the signal from said differentiating means, said zero-crossing detector providing an output pulse each time the signal from said differentiating means crosses a zero reference level;
• direction determining logic means for receiving signals from the zero-crossing detectors of said first and second channels and for providing at its output a signal indicative of the direction of the vehicle travel along said path depending upon which of said zero-crossing detectors produces the first output signal, and;
• vehicle counting logic means for receiving the signal from the differentiating means of said first channel and providing an output indicative of the number of vehicles passing along said vehicle path past said predetermined point.