HADECS 3 (Highways Agency Digital Enforcement Camera System) are radar-based speed cameras currently used on intelligent highways with variable speed limits. The cameras are on the opposite side of the street, about halfway up a bridge post. These cameras are often very difficult to spot due to their size and lack of bright colors. The HADECS 3 cameras can monitor all lanes of traffic and are linked to a central computer system that adjusts settings depending on changes in the speed limit on the highway. 
When the speed limit signs on the bridges over each lane change, the camera angles change with them. If a vehicle is speeding, 2 photos are taken (to allow for manual checks if needed) then the high quality imaging allows the software to identify the vehicle details and issue an intended law enforcement notice. 
There are a few Smart Motorways in operation, more under construction and more planned. It is inevitable that these cameras will become more and more popular in the fight against speeding drivers.
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