Traffic lights aren't always as mundane as stop and go. I've noticed some pretty puzzling lights recently, as have you, my readers - odd phenomena such as flashing yellows, missing green arrows, and bizarre sequencing.
We investigate a few of these strange birds in today's piece.
The missing arrow
Charlie Fox, a Jamaica Plain resident, couldn't quite figure out what was going on.
Driving south on the Jamaicaway, he came to the Pond Street intersection, where there's a green arrow signal for left turns. Cars sometimes would line up in the left lane, waiting for the green arrow - but it never came.
A whole light cycle would go by, and no green arrow. Then another light cycle, and still no arrow. Oher times, the green arrow would work just fine.
"Often, oddly, it seems not to be working during rush hour when it is most needed," he wrote in an e-mail. "Is this intentional, or a malfunction of some sort? If it is an effort to keep traffic moving during rush hours, it is having the opposite effect."
The contractor who is remodeling Fox's house, Rod Fountain, chimed in with a theory (as contractors often do): sensors in the pavement, installed to detect left-turning cars, were malfunctioning.
The traffic light is controlled by the state Department of Conservation and Recreation, which inherited it from the old Metropolitan District Commission. Spokeswoman Wendy Fox (no relation to Charlie Fox) said that, indeed, changes have been made to the operation of the light.
In the lingo of traffic engineers, green arrows can either be "leading" or "lagging," she said. Leading arrows come before the green circular lights, when more people expect them, while lagging arrows come after circular greens have turned to red. The Jamaicaway-Pond Street intersection's arrow was changed to a leading arrow about a year ago to improve pedestrian safety.
To properly credit Fountain, that was part of his theory, too. His guess about pavement sensors triggering light changes was accurate as well.
("That is a very smart contractor," Wendy Fox said.)
However, the sensors were deactivated a year ago when the arrow was switched. "Under the current operation, the green arrow comes on for 15 seconds between 3 and 7 p.m., Monday through Friday. It's on for only eight seconds at all other times," she said. There is never a time, she said, when it shouldn't come on.
DCR crews who inspected the green arrow last week reported that it was working fine. It would appear that the glitch is gone.
Out of sequence
I, too, have had a strange encounter with a left green arrow, at the intersection of Walden Street and Massachusetts Avenue in Cambridge.
This green arrow is a lagging arrow, meaning it comes after the green circular signals have turned to red. Everything is normal until the point the arrow turns to a yellow. At that moment, every yellow on my side of the road - not just the yellow on the arrow's set of signal lights - turns to yellow, too.
If you're waiting at the red light to go straight on Massachusetts Avenue, the light changes from red to yellow, then back to red when the arrow's set of signal lights turns red. I've seen drivers wise to the light hit the gas on the false yellow and get through the intersection before it flips back to red.
Sergeant Michael Maffei of the Cambridge Police Department's traffic unit said there is no way traffic lights should operate that way.
"The cycle should be green, yellow, red. It sounds like an anomaly. A malfunctioning light," he said.
But do drivers have the right to shoot through on the false yellow, I asked?
Maffei reminded me that, contrary to common practice in our crazed driving culture, you're not supposed to speed up at a yellow light. The law says you're supposed to stop, just like it's a red light.
"Unless it is unsafe to do so, you're supposed to stop at a yellow light," he said.
"If you're stopped, and the light went to yellow, it's the same as a red. You could still be stopped by the police. Chapter 89, Section 9, $100 fine. Failure to stop for a mechanical device."
Flashing yellow
Our last example is more basic than the others, but still caused me some confusion. Driving on the back roads of New Hampshire this summer I came upon a four-way intersection with a single, flashing yellow light hung by wires over the center of the road. Cars on the cross street, which was the smaller street, were stopped as I came to the intersection. Not knowing what to do, I sailed on through.
Should I have stopped, too?
"Whenever lights are set like that," Maffei said, "the main road will usually have a flashing yellow, the side road, a flashing red. The main thoroughfare will always have a 'proceed with caution,' and the side street that enters it will have a 'stop and proceed.' You should have slowed down."
I made a mistake in last week's column, misinterpreting state law regarding teenagers and seat belts. The Registry of Motor Vehicles driver's handbook is entirely correct in saying that drivers can be fined $25 for each person age 12 to 16 who isn't wearing a seatbelt in the car. Teens 16 and older are responsible for paying their own fines.
