Thinking of us

[lesiz]

I've never seen this, and was surprised to see these cutouts in the BIKE LANE for traffic signal sensors!

This is in SoCal on Palos Verdes Drive at Hawthorne Blvd.

I wonder if the LA County traffic engineers know that most bikes along this route are with either aluminum or carbon frames, neither of which are known for their magnetic properties.

Or -- maybe the sensor is sensitive enough to trigger off the chain.

In any case, I'm encouraged by the fact that the traffic engineers consider the bike traffic important enough that they gave us our own sensor!

http://i163.photobucket.com/albums/t306/lesiz/HPIM0949.jpg

[crhilton]

I'm guessing it's there for cars and the lane was changed to a bike lane later on...

Some cities use camera to detect cyclists.

[CaptainCool]

I'm guessing it's there for cars and the lane was changed to a bike lane later on...
Nope, that one's bike-specific. The ones for cars are as wide as a car.

They're all over the bay area. Some look like little diamonds, but they have the same cutout traces.

And they rely on the metal in your wheels, not your frame.

[Tude]

Huh, look pretty fresh too. Almost looks like an error?

<edit> but after some thought - does seem interesting. Were you able to trigger it?

[BikeManDan]

I'm guessing it's there for cars and the lane was changed to a bike lane later on...

Some cities use camera to detect cyclists.

No way the perfect spacing between the bike lane lines is a coincidence

[The Human Car]

Some cities use camera to detect cyclists.

And some cities turn the sensitivity down on cameras (as well as loop detectors) so they don't get any "false" positives when a cyclists pulls up. :mad:

[CB HI]

...
I wonder if the LA County traffic engineers know that most bikes along this route are with either aluminum or carbon frames, neither of which are known for their magnetic properties.

Detection of Bicycles by Quadrupole Loops

http://www.humantransport.org/bicycledriving/library/signals/detection.htm

How to Turn Signals Green

http://www.humantransport.org/bicycledriving/library/signals/green.htm

Edit: links fixed.

[Eli_Damon]

My understanding is that aluminum frames don't have a problem triggering the detector but that carbon frames do. However, I don't know why anyone would be installing new loop detectors. I thought that everyone was switching to camera detectors.

[genec]

Those are BL loops alright... we even have a few here in newer areas of town... however their sensitivity may or may not be set correctly... I've waited at a couple of lights far too long with the expectation that the light will change.

I should report these to the street division... but in the past I got a "job closed" response and the darn things are still mucked up. I have little faith in these.

[John E]

My understanding is that aluminum frames don't have a problem triggering the detector but that carbon frames do. Correct. Ferromagnetism is not required, since the loops work by inducing electric current in the object being detected. Because the loop's electric field falls off rapidly with distance, the detector responds primarily to your wheel rims. My technique for triggering a circular CalTrans D loop is to stop with each rim and one pedal directly over the arc of the last loop before the intersection.

However, I don't know why anyone would be installing new loop detectors. I thought that everyone was switching to camera detectors. That definitely is the trend, but camera detectors have problems under foggy conditions.

[noisebeam]

There are bicycle specific ones in the bike lanes at some intersections where I live.

But they are totally useless as I rarely will be in the bike lane at those intersections unless I am turning right!

Actually they are worse than useless as now the city no longer must ensure the sensors in the thru lane work for bicycles.

Al

[noisebeam]

My understanding is that aluminum frames don't have a problem triggering the detector but that carbon frames do. However, I don't know why anyone would be installing new loop detectors. I thought that everyone was switching to camera detectors.

A single aluminum wheel will trigger the bike lane loop detectors and many of the non-BL loop detectors with careful positioning.

Al

[CB HI]

Links fixed above to:
Detection of Bicycles by Quadrupole Loops

How to Turn Signals Green

I have also found that lifting the front wheel a slight amount and swinging it (left & right) across the saw cut will improve detection.

[crhilton]

Nope, that one's bike-specific. The ones for cars are as wide as a car.

They're all over the bay area. Some look like little diamonds, but they have the same cutout traces.

And they rely on the metal in your wheels, not your frame.

I thought almost all wheels were aluminum.

[Helmet Head]

My understanding is that aluminum frames don't have a problem triggering the detector but that carbon frames do. However, I don't know why anyone would be installing new loop detectors. I thought that everyone was switching to camera detectors.
Frame material is irrelevant... it's the rims that are closest to the loops and are what trigger the detector.
On loop detectors put your room on the loop at a tangent to the circle.
On double loops put one wheel in each loop. On the one pictured in the OP, I would straddle it at a diagonal such that one wheel is inside the left one and the other wheel inside the right one.

[Helmet Head]

I thought almost all wheels were aluminum.
Right. And aluminium is conductive and so triggers the detector if placed correctly.

[noisebeam]

Right. And aluminium is conductive and so triggers the detector if placed correctly.

That's right. I've been saying this for a while now - I rode around my neighborhood one early Sunday morning when there was close to no other traffic and tested about eight sensors. I parked my bike on the side of the road, took of front wheel and walked to sensors and held wheel vertically (just as if you were on bike) on top of center of dipole sensors and all of them triggered due to the front wheel alone.

Al

[Bekologist]

bike specific loop detectors in bike specific lanes at major intersections are a step in the right direction for communities interested in better accomodating bicyclists in the transportation grid.

In Seattle there are both bike specific detectors at some intersections, and bike 'marks' indicating the sweet spot over the detectors in main travel lanes at more minor intersection not treated with thru bike lanes to the left of RTO traffic. The city is open to adjusting sensors and marking the sweet spot for bicyclists here.

[noisebeam]

bike specific loop detectors in bike specific lanes are a step in the right direction for communities interested in better accomodating bicyclists in the transportation grid.

In Seattle there are both bike specific detectors at some intersections, and bike 'marks' indicating the sweet spot in main travel lanes at more minor intersection not treated with thru bike lanes to the left of RTO traffic.

Putting bike specific sensors in BLs to the left of RTOLs is somewhat useless. The only time they would need to be activated is when there is no other traffic in which case there is no reason to be in the BL and in fact good reason to be out of it.

marking the sweet spot for bicycles for sensors that are shared with motor vehicles is a good idea.

Al

[Bekologist]

al, having a bike specific vehicular lane that does not contradict the rules of the road should not be ignored by a thru bicyclist rolling up to major intersections.

why you think this is the case speaks of substandard road design, not bicycling imperatives.

a wide and accomdating bike lane that has a sensor for bikes to the left of RTO lanes? ABSOLUTELY a good idea. a bike rolling up first begins the sequence.
a rider that understands the appropriate use of well implemented bike facilities uses the lane to pull up to the stop. why risk being rear ended in the travel lanes?
additionally, during typical commute times, the sun is often low in the sky, often compromising the visibility of a bike in a travel lane stopped at a light.

why you erronously insist a bike should be out of a well provided bike lane approaching a major intersection- that is hardly the case, and less so as improved intersection designs better accomodate bicyclists-

the sensors and bike lanes illustrated by the OP are likely part of a well implemented road network of bike lanes that do not need to be ignored as a bicyclist approaches the intersection.

[noisebeam]

that is why i said 'somewhat useless.' i agree many cyclist will find use of them (The ones in BL left of RTOL) , but as far as implementing good light sensors, putting them in BLs avoids the issue of making sensors marked and working for all destinations.

[lesiz]

Huh, look pretty fresh too. Almost looks like an error?

<edit> but after some thought - does seem interesting. Were you able to trigger it?

At the time of day that I reach this place, there's plenty of auto traffic so the signals are pretty busy anyway. However, if I get in the left-turn lane I have to wait for a car to come along behind me to trigger the thing. Presumably the bike lane detector is more sensitive.

[donnamb]

Presumably the bike lane detector is more sensitive.
It should be, and if it's not, call your city bike planner's office, or whoever does the bike stuff on the roads. Those detectors can be adjusted.

[lesiz]

...and then, farther down the road from this traffic signal, farther down on Palos Verdes Drive there's this:
http://i163.photobucket.com/albums/t306/lesiz/147460.jpg
There's 2 things wrong here. First, the obvious bass-ackwards "N".
Second thing wrong: The guy who stopped on his bike to take the picture was new to using shoe clips. He came to stop, THEN, he thought, "THE CLIPS, THE CLIPS! Aaaaaaaaa"
My shoulder is still sore from that one.

[ChipSeal]

"Second thing wrong: The guy who stopped on his bike to take the picture was new to using shoe clips. He came to stop, THEN, he thought, "THE CLIPS, THE CLIPS! Aaaaaaaaa"
My shoulder is still sore from that one."

Great commentary! :p It is kinda hard to see in the picture from that angle. Thanks for sharing, it made me laugh. (I have never done such a thing myself, of corse... with four or five exceptions!)

[sc0ch]

These quadrapole detectors are in Berkeley, and they are highly erratic. Better than nothing. The camera's can be frustrating too, but maybe I'm just impatient.