Car Park Count Systems
Vehicle Counting Overview
Vehicle counting is becoming a common requirement for car parks regardless of their size. It is a great convenience for visitors to be aware of the number of available spaces before they enter a car park or venture into another section of the car park. Traffic monitoring on roads is also becoming commonplace as highway authorities and council transport departments strive to reduce congestion.
For vehicles to be automatically counted, there needs to be a means of detecting them. The most common form of vehicle detection uses an inductive loop buried in the road surface. As a vehicle passes over the loop, the loop inductance changes causing the loop monitoring circuit (loop detector) to output a signal. If two such loops are placed close together along the path of the vehicle, the direction in which the vehicle is travelling can also be detected. In car park applications, loops need to be placed in each entrance and exit lane as well as on ramps between levels. The counting system receives the signals from the loop detectors and maintains a count of vehicles entering and exiting each area. It then computes the date as necessary to provide the required display information and / or alarm signals.
Typically, the count system will provide comprehensive on-screen information to the management and / or display count values at key locations around the car park using Variable Messaging Signs (VMS). The counting system may also have ‘count thresholds’ set so that it can raise an alarm whenever a count reaches a critical value.
Simple Space / Full Display
Many counting systems simply need to keep a record of the vehicles entering and leaving a car park and to display a ‘FULL’ sign at the entrance when there are no free spaces. The entry barrier must be prevented from allowing vehicles to enter while the sign shows ‘FULL’. When the car park is empty the count value is set to the total number of parking bays. As each vehicle enters the car park the count is decremented. As each vehicle leaves the car park the count is incremented. When the number of vehicles in the car park equals the total number of spaces, the sign at the entrance displays ‘FULL’. At all other times the sign will display ‘SPACE’. The counter prevents the barrier control from allowing vehicles to enter while the sign shows ‘FULL’.