OK, it is time for a mea culpa. That’s right, write this down because I am here to apologize. In my August 27 blog entitled “Cameras or Sensors?” I took the side of sensors. I argued that sensors are much less expensive than cameras and provided far more information. To my mind that has not really changed but video has come a long way in recent years and deserves a second look.
Recently, one of the most important developments for our industry is in quality digital video recorders or DVRs. They have become relatively inexpensive yet offer an incredible amount of storage. Before these became available, you had to react to alarms (provided by sensors) when the problem occurred to view the video. You wouldn’t necessarily understand how the problem developed but at least you could see what the problem was and formulate a response. So, at that time, the value of video was more reactive.
Now you can go back in time and watch how the problem developed. What happened to cause it? Was it an errant driver? Or did traffic control contribute to the problem? In other words, you can use stored video to improve upon your traffic control. It has become proactive, rather than simply reactive.
Wireless service has become more dependable and 4G service offers good bandwidth if you need streaming video but it can be expensive. And in most cases you won’t need that. A few frames a second will provide all the real time information you need to understand what is happening in a work zone. Use the money you save to add more devices or to use these systems in additional work zones.
Another change is the variety of cameras. Most manufacturers offer good 12 volt cameras now. And you may choose from color, black & white, infrared, or some combination of all three. They run from very basic “grainy” video to high quality megapixel video. The more basic the video, the more you can store on the DVR. High quality video is great, but takes far more storage space. You must evaluate that trade-off between video quality and storage. Most DVRs will begin recording over the oldest video when it is full. So the question becomes, “When an event occurs, how soon must I download the video before it will be lost?” In most cases you can design a system with 30 days storage, giving you plenty of time to find out about a problem after the fact and still go back and view it.
Cameras now offer a few more bells and whistles that may also be of interest. They can be set to scan a work area continuously. Or they can be set to focus on a particular area during morning drive time and another area late at night. This feature might improve security where theft or vandalism is a problem. Alarms or flashing lights can even be triggered when movement is detected late at night.
This feature could also be used to leverage your work zone ITS dollars. If traffic is heavy in only one direction at a time, one camera could be used to view both directions of traffic. In the morning it could view the traffic heading into town and in the afternoon it could be set to switch automatically to the outbound direction.
Cameras can still be manipulated manually. Any time a new alignment is installed, particularly lane shifts or crossovers, you should monitor traffic through it to be sure drivers understand what is now expected of them. If they handle the change well, you can pat yourself on the back for a well designed work zone. But if problems develop, you will know you need to make adjustments.
Cameras are still several times more expensive than sensors. Sensors must provide the data backbone of any good work zone ITS system. But stored video can be another useful tool in your tool box…especially when analyzing problems and making improvements in traffic control design.