NEWS-LEDGER — MARCH 6, 2013 –
By Steve Marschke
Have you ever seen those gizmos mounted on West Sacramento traffic poles, and wondered if they’re cameras? And, if so, who’s watching you?
There are at least three types of pole-mounted sensors around town at different street intersections. And Peter Hanson, an engineering assistant with the City of West Sacramento’s Public Works Department, reminds us that none of them is a “red light” camera. The city doesn’t currently have a “red light camera” program to catch red light runners.
So what, exactly, are these devices?
At the corner of Jefferson Boulevard and Stone Boulevard, near the railroad tracks, you may see a thing that looks like a hanging bulb. It’s one of several security cameras operated out of the Port of West Sacramento, which is serviced by the railroad.
“These cameras have a dual purpose,” reported Hanson. “’A,’, to observe the intersection (for security), and ‘B,’ to observe the traffic at the intersection.”
Aside from monitoring security, the camera’s view can be used by city staff to see how traffic light timing changes are affecting the flow of traffic, for example.
Another type of “camera” seen at some traffic-light controlled intersections is a long, white cylindrical device. Those are directly linked to the traffic light controls.
“Those are video detection systems,” explained Hanson. “It knows if a car is coming or not. It actually sees cars, and changes the light for them. It ‘sees’ through algorithms, and it looks at the differences in contrast” in its field of view.
Then there are the more numerous little black items mounted on many a local traffic light pole.
“That’s a detector for emergency vehicles,” said Hanson. “If you look at an emergency vehicles, you will see a light bar on the roof, and in the center, there is a white strobe light. In our city, the fire and police vehicles each have one.”
Those strobes on top of fire trucks and police cars can, when turned on, put out a pattern of white flashes – which is picked up by the traffic pole sensor, and earns a “green light” for that Code 3 emergency vehicle.
Ambulances serving the town can’t do this trick, said Hanson.
There’s at least one other smart gizmo on the street – or under it, to be precise. An “induction loop” can be buried in the pavement to sense the magnetic presence of a car that has pulled up to a red light, signaling the traffic lights that they need to change.
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