One of the most popular ways to detect vehicles for triggering the opening of barriers, bollards or gates are inductive loops sealed into the surface of the road near the access point. The sub-surface loop is connected to a ProLoop loop detector which measures the change of inductance in the loop, as a vehicle approaches the change in inductance is detected and the output of the unit changes providing the trigger signal for a gate or traffic light. These units detect any metal objects such as pedal bikes, motor bikes, cars, vans, lorries and fork lift trucks.
An alternative way to installing inductive loops is a Herkules microwave motion sensor. These can detect the vehicle (or person) approaching or leaving the access point. They have the advantage that the road does not need to be cut to install inductive loops, but it is important to not that they are only triggered by movement. They can be programmed to detect the difference between people and vehicles or the direction of travel.
Another detection method is ultrasound sensing found in the USVD Driv Thru Vehicle Sensor. This unit detects the presence of a vehicle in a drive through lane, like the microwave motion detector it is much less expensive than loop detectors. The USVD is simply mounted on a post and aimed at the location where a vehicle would pass.
The most simple method of detecting the presence of an object, is a simple photoelectric sensor. The output of these devices change when their beam is broken by a vehicle or person. They cannot detect the difference between a vehicle or person, but are a simple way to triggering a gate as part of an overall control system.
All of the above methods are complemented by our range of DokTek LED Traffic Lights. The Ultra-Bright LEDs used in the traffic lights are idea for use in bright sunlight and of course in the rain of our British climate! They are simply controlled by providing a 24Vdc power supply to the LEDs and in conjunction with the Traffic Light Control Board, either with or without vehicle sensing, provide a simple traffic control solution around car parks and factories.