A traffic camera is a video camera which observes vehicular traffic on a road. Typically, these are put along major roads such as highways, freeways, motorways, autoroutes and expressways, as well as arterial roads, and are connected with optical fibers buried alongside or even under the road, with electrical power either provided by mains power in urban areas, or via solar panels or another alternate power source which provides consistent imagery without the threat of a power outage during inclement conditions. A monitoring center receives the live video in real time, and serves as a dispatcher if there is a traffic collision or some other disruptive incident or road safety issue. Traffic cameras are a major part of most intelligent transportation systems. They are especially valuable in tunnels, where safety equipment can be activated remotely based upon information provided by the cameras and other sensors. On surface roads, they are typically mounted on high poles or masts, sometimes along with street lights. On arterial roads, they are often mounted on traffic light poles at intersections, where problems are most likely to occur. In remote areas without easy reach of the main electrical grid, they are usually powered by another means such as solar power, which also provides a backup source to urban camera infrastructure. Traffic cameras are distinct from road safety cameras, which are put in specific places to enforcerules of the road. Those cameras take still photos in a much higher image resolution upon a trigger, whereas traffic cameras are simply for observation and constantly take lower-resolution video, often in full motion, though they are remotely controllable in order to focus on an ongoing traffic incident farther along a road that may not be in the camera's usual field of view or even along a frontage road or other roadway within its field of vision. Many transmit in the legacy analogNTSC and PAL formats, depending on location, though many are being converted to high definition or 4K resolution video as equipment is replaced. Some have a compass built in which displays the cardinal direction at which the camera is aimed, though many providers also provide a reference image of a shot with the cardinal direction. Many transportation departments have linked their camera networks to the Internet on online websites, thus making them webcams which allow commuters to view current traffic conditions. They may show either streaming video or still imagery which refreshes at a set interval of seconds or minutes, helping travelers determine whether an alternate route should be taken. In the United States and Canada, these often are displayed on state or municipally-run 5-1-1 websites. These traffic images are also combined with road sensors which measure traffic timing to provide a full picture of traffic conditions. Many states and provinces consider this information public domain, thus many television stations air live traffic camera imagery during their own traffic reports on their local news broadcasts, or simply as an augmenting moving visual background during newscasts. Some cable TV systems provide these pictures full-time on a governmental access channel, and some broadcast stations set aside a full digital subchannel solely for traffic information and camera imagery, such as Philadelphia's WPHL-DT4 in the past and WMVT-DT3 in Milwaukee and WFMZ-DT2 in Allentown, Pennsylvania currently. However, in some cases for toll roads and other private road authorities, such as the Illinois State Toll Highway Authority, these images are claimed to be the property of the toll agency, and the images are held under an exclusivity agreement for one station.
