Industry spotlight: Traffic Surveillance Cameras
If you live in a city or large town, chances are you've seen their footage on the news or noticed them on the freeway - traffic surveillance cameras are commonplace now on major arteries. In the United States, nearly every state has a dedicated arm of their department of transportation which maintains and monitors surveillance cameras on major roads, interstates, freeways and highways.
These cameras are used solely for monitoring traffic patterns, mostly during rush hours and times where traffic is at its peak. Often placed at congestion areas and high-traffic locations, the feed from these cameras are often influential in future road planning and future policy decisions involving speed limits and other traffic laws.
Surveillance cameras are also useful, especially in large cities, for traffic reports generated by local news outlets. Often, a TV news station will broadcast the feed directly, giving viewers the opportunity to preview the traffic conditions before they leave the house. Radio stations also use these as a basis for their traffic broadcasts. While traffic patterns are usually the same from day to day, a major accident or road obstruction can cause huge traffic backups. The traffic broadcasts and advisories can help prevent commuters from being late to work and other appointments, allowing them to plan an alternate route if traffic is particularly bad.
Stoplight and Speed Camera Systems
Camera systems which record moving violations, such as running red lights or speeding, have become popular law enforcement tools for municipal governments in recent years.
Red light cameras, the more popular of the two, are placed atop traffic signals at popular or busy intersections. Traffic cameras like these are usually regulated from town to town, and the types of cameras used and the enforcement of the system is highly varied.
A red light camera system consists of cameras (usually placed at each corner of the intersection, although they are sometimes placed atop the signals themselves or on their poles), a system of inductive wire embedded beneath the asphalt, and a computer system which is usually mounted on a pole nearby. When a car runs a red light, it passes over the inductive wires and generates a magnetic field which alters the current generated by the wires. This current change triggers the camera to take a snapshot of the car as it passes through the intersection. This photo is used to generate a ticket based on the offending license plate number, which is mailed to the registered owner of the car.
Another type of surveillance camera, although less widely used than red light cameras, is the speed camera. Speed cameras use several different types of technology, most commonly lasers or radar, to pinpoint cars that are exceeding the marked speed limit, and work much in the same way that red light cameras do. When a speeding car is detected, the radar or laser signal triggers the camera to record the car's license plate and that data is used to issue a ticket to the car's owner.