Off-the-shelf video cameras work in many traffic situations, but cameras with additional capabilities are often needed where environmental, geographical, or task-specific considerations apply on the road. Environmental enclosures are an integral part of a traffic closed circuit television (CCTV) system, and are distinct from the common security-market housing. Nearly 80% of all US Departments of Transportation specify a pressurised enclosure to increase camera reliability and reduce maintenance costs. Digital signal processing (DSP) is a recent traffic adaptation of camcorder technology. It can `electronically magnify' the scene produced by the camera, which makes the image easier to view and interpret, when looking at a monitor from a distance. This feature is useful up to fourfold magnification. A DSP camera also has an RS232 or RS422 interface, which connects it to the computer at a traffic operations centre, and enables its operator to control several camera operation parameters remotely. The extended intrascene light range camera, also known as `wide dynamic range', is now affordable and is used to identify licence plates in California. The Cohu and Progressive Scan CCTV cameras also have useful traffic control applications.
Abstract