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Old 08-02-09, 03:31 PM   #1
rcy84
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Left Turn Traffic Light

Hello, everyone. Newbie here. Just had a question regarding left turn traffic signals. Do they "sense" bicyclists in the left turn lanes just as they do cars? I ask this because my brother and I were riding at night (with all proper lights and equipment), and pulled into a left turn lane at an intersection but waited there for so long that we just decided to do a box turn. I'm not sure if traffic lights function differently depending on the area.

P.S. Sorry if this subject has been brought up before. I tried doing a search, but all I caught was threads about proper lane-changing techniques and safety issues regarding left turns at intersections.
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Old 08-02-09, 03:41 PM   #2
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Traffic light sensors commonly activate by detecting an automobile's mass of metal through an inductive coil loop embedded in the asphalt surface. Bicycles, and often motorcycles, don't have enough metal mass to trip the sensor.
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Old 08-02-09, 03:47 PM   #3
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contact the city about it.
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Old 08-02-09, 04:11 PM   #4
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Yes, do contact the city about it. Making box turns is the safest way to get across the street but I would have just crossed over without the light changing if it were safe. I ride a scooter and experience the same thing from time to time. I will either jump out of the turn lane and get into the furthest left lane and make a u turn or run a red light as I did about two weeks ago.
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Old 08-02-09, 06:39 PM   #5
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Might be obvious, but if there is a crosswalk, there are sometimes buttons that can be pushed to help trigger the light change.
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Old 08-02-09, 06:42 PM   #6
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Might be obvious, but if there is a crosswalk, there are sometimes buttons that can be pushed to help trigger the light change.
I have to do that every once and a while, oddly one time the light still didn't change.
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Old 08-02-09, 07:07 PM   #7
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I can consistently trigger almost any traffic signal loop detector I can see. Look for the circular, square, or octagonal outline, then stop with each tire contract point over a point on the final detector before the intersection. Assuming you have either aluminum or steel rims, you will be detected if the loop's sensitivity has been set high enough by your local traffic engineer. If you are certain you are unable to trigger a particular traffic signal, be polite but persistent about reporting it. I have had extremely good results with the City of Encinitas, where I live, and even better response (so to speak) from the City of Carlsbad, where I work.

Don't take "no" for an answer -- any of the newer-technology CalTrans type D or E loops can be adjusted to detect the bottoms of your aluminum rims.
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Old 08-02-09, 07:51 PM   #8
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I've found a couple of the above-mentioned loops that don't pick up my rims, but they'll pick up my frame if I lay it down. As soon as the cross-traffic light turns yellow you can hop on your bike.

This works great unless you flounder (like me) trying to get clipped in in a hurry.

This can also get awkward if a car comes up behind you but doesn't pull far enough forward to trip the sensor.
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Old 08-02-09, 08:11 PM   #9
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Most intersection loop sensors will be triggered by my bicycle, but for the ones that aren't activated the first time, I'll circle around a couple of times if no car is traveling in my direction, and making sure beforehand that I have enough room to circle around. Here locally, there is a loop sensor about a block before the traffic light, so there's no need to have a vehicle pull up to the front loop sensor at the intersection in order to activate the traffic light.
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Old 08-03-09, 12:26 AM   #10
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Wow. Thanks for the great responses. I will definitely try everything mentioned. Now I know what those markings near intersections in the asphalt are for. Will try proper wheel placement, laying bike frame closer to ground, and circling. Will definitely contact the city to report "bad" left-turn intersections. Thanks for all the help!
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Old 08-03-09, 05:16 AM   #11
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Check your laws, too. Here I can carefully go through a red if my motorcycle doesn't trigger it. I know of only one light this happens with. I don't actually do that, I just turn right and do a turn down the road. I don't know whether this applies to bicycles, but I would see it as a reasonable interpretation of that particular law.
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Old 08-03-09, 08:34 AM   #12
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How to Turn Signals Green
http://www.humantransport.org/bicycl...nals/green.htm



Detection of Bicycles by Quadrupole Loops at Demand-Actuated Traffic Signals
http://www.humantransport.org/bicycl.../detection.htm
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Old 08-03-09, 12:58 PM   #13
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Quote:
Originally Posted by Scrabbler View Post
Might be obvious, but if there is a crosswalk, there are sometimes buttons that can be pushed to help trigger the light change.
I've never figured out how that's supposed to help. Here I am, in the left turn lane, and the light doesn't change. I'm supposed to dismount and walk, or ride, 20 feet over across at least one lane of moving traffic (or bumper-to-bumper stopped cars, probably with the front one nosed way out into the intersection and which might start moving at any time) to push the button, then make my way back to the turn lane to wait for it to change?

Also, around here, triggering the pedestrian signal does NOT trigger the left turn signal. That only triggers if there's a vehicle in the left turn lane.
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Old 08-03-09, 01:11 PM   #14
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Quote:
Originally Posted by rcy84 View Post
Hello, everyone. Newbie here. Just had a question regarding left turn traffic signals. Do they "sense" bicyclists in the left turn lanes just as they do cars? I ask this because my brother and I were riding at night (with all proper lights and equipment), and pulled into a left turn lane at an intersection but waited there for so long that we just decided to do a box turn. I'm not sure if traffic lights function differently depending on the area.

P.S. Sorry if this subject has been brought up before. I tried doing a search, but all I caught was threads about proper lane-changing techniques and safety issues regarding left turns at intersections.
Some sensors are sensitive enough to detect a bicycle or motorcycle some are not. Sounds like you hit one that isn't sensitive enough. I would note it's location and contact your local Bicycle and Pedestrian Safety Coordinator's office. If there isn't one I would contact the your mayor's action line and/or your state DOT to have it replaced the next time they do major repair work on that road.
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Old 08-03-09, 01:13 PM   #15
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I'm with theBugGuy. At intersections with not-so-sensitive loops, I'll hold my bike by the nose of the saddle laying it down to the right pretty low (I have monkey-like long arms, which helps) so that the large mass of metal that is comprised of the cranks and bottom bracket hovers over the cuts.

Many intersections have sensors that will pick up a bike standing up. Some intersections 'round town have a pair of painted lines that designate where you should place your wheels to allow for sensing.
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Old 08-03-09, 01:33 PM   #16
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not in irvine they dont.
I dont even bother waiting at some lights...i go over to the pedestrian cross walk and hit the button.
it depends on the intersection tho. the more popular intersections will turn green no matter, but many of the less traveled crosses will never turn green.
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Old 08-04-09, 08:31 PM   #17
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In the city where I used to live, most of the major intersections were loop-detected. In the daytime it wasn't a big deal because there were always cars to trigger it. The only problems were when the car behind me gave me too much room and didn't pull up over the sensor. That can be solved by edging forward or with a hand gesture.

Night time was a different story. I was often the only vehicle on the road, and the busier street always had the green light. I tried everything I could, on several occasions, but never could trigger the sensor. Finally I just gave up. If traffic was sparse I began treating those lights like stop signs. Sometimes that's all you can really do. By the way, there weren't even pedestrian crossing buttons to use as a last resort. This was in a very pedestrian-unfriendly city with hardly any controlled crosswalks.
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