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Triggering the green light 101
Dear Street Smarts, Q: Every time me and my buddy, TrugDog, come to a stop light, he bugs me to 'move up a little bit' to 'activate the sensor,' as if there is some hidden sensor to activate the green light or turn signal. I think this is delusional or very optimistic on his part. What's the word on these 'sensors?' Do they exist? If so, are they contained in the road or in the traffic lights. Until I hear otherwise, I am gonna stay a safe five feet back from the stop line. Please run your reply in the Sentinel! Love your column! Arturo Coon, via email A: You may want to move up about four feet to trigger the sensors on the road, as the portion closest to the limit line is the most sensitive, according to a local expert. “Sensors for detecting vehicles at traffic signals are set up to align with the limit lines,” said Jack Sohriakoff, senior civil engineer for county public works. For the county's traffic signals, “there are generally four separate in-pavement loops in each of the travel lanes at the intersection – left turn, through, or right turn lanes -- but the one closest to the limit line is more sensitive,” he explained. “The closest one is set one foot back from the limit line. Each loop is about 6 feet by 6 feet square and centered in the travel lane, and they are approximately 10 feet apart. Doing the math, the loops begin approximately 55 feet from the limit line. This does not include the advance loop which can be up to 250 feet in advance of the limit line.” If a traffic camera is used to detect vehicles, “the 'zone of detection' is a rectangular area similar in shape as the four in-pavement loops would normally provide,” Sohriakoff added, while encouraging motorists to pull as close to the limit line as it's safe to do so while straddling the middle of the travel lane. Those of you who do not drive cars may be asking, "what if I'm traveling on a motorcycle or bicycle?" Lt. John Hohmann, of the Scotts Valley Police Department, has been riding motorcycles for years, both on and off the job. He tries to position his engine block directly over the sensor's loop to trigger a green light, he said. Meanwhile, check out this advice for cyclists from this May 2011 Street Smarts guest blog offered by Cheryl Schmitt, bike coordinator for the city of Santa Cruz: http://www.santacruzlive.com/streetsmarts/2011/05/09/bicycle-detection-at-traffic-signals/.
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