Early violation enforcement system (VES) implementations relied on high resolution CCD cameras with moderately high shutter speed and supplemented by high intensity, continuously-on lighting, effectively equivalent to flood lighting. The technology has evolved to progressive scan cameras that capture a full instead of partial image frame and are capable of very high shutter speed to handle higher vehicle speeds.
The majority of vendors are now implementing pulsed or flashed, high intensity LED white lighting and infrared lighting, although some implementations measure ambient lighting and supplement with continuous lighting as needed to successfully perform optical character recognition on the captured image. Cameras can be mounted either overhead or along the side of the toll lane(s). Only when the camera is mounted on a toll island or top of a concrete barrier does it pose potential safety and operational concerns, particularly when visible to the user. If the camera is visible, regardless of location, the user may maneuver their vehicle in an unsafe manner in an attempt to avoid the capture of their license plate, subject to physical constraints preventing such action. Similarly, supplemental lighting can be mounted either overhead or along the side of the toll lane(s). However, for supplemental lighting both mounting locations pose potential safety and operational concerns.
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