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Video detection “sees” vehicles by using cameras to detect changes in pixels. Some people believe that the cameras, which are usually placed on signal arms, take actual video, catalog images or provide real-time images — this is not the case! When the system works it is great, but when it fails you get stuck at a light. This is an example of one of these systems failing and how to correct it with a light shinned directly at the said camera.
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Blub from an article about a system in Clovis, New Mexico:
A computerized control system that uses sensor cameras to control traffic at intersections. How it works: The light stays green on the main throughway until vehicles approach from side streets. When vehicles from the side streets approach, the light turns green for them and remains green for about 7 seconds. If more time is needed, the system is programmed to allow for it. What was the system before: Before the camera sensors were installed, the city had a loop system underneath the pavement that could sense metallic objects and convey that to the signals. Over several years, the pavement can shift and cause the system to malfunction. There are still loop systems in the city in use. Drawbacks: The cameras can malfunction in bad weather or in direct sunlight.
More info, search Google: Autoscope Solo Terra
https://www.fhwa.dot.gov/policyinformation/pubs/vdstits2007/05.cfm
Basics of how it works seeing pixel changes.
Downstream Viewing.
* Camera on overpass concealed from drivers.
* More information from tail lights available for braking indication, vehicle classification, and turning movement identification.
* Easier to acquire vehicles that are closer to the camera for the tracking algorithm application
* With visible imagery, more information is available to a tracking algorithm from tail light viewing
Upstream Viewing
* Headlight blooming, glare on wet pavement, headlight beams detected in adjacent lanes on curved road sections
* More blockage from tall trucks
* Traffic incidents are not blocked by resulting traffic queues
* With long wavelength infrared imagery, similar information is available to a tracking algorithm from headlight and tail light viewing
See my other video
Post time: Jul-22-2017