I fucking ABHOR protected left turn arrows

[roadman65]

I agree just switching them to flash mode and obtaining the software is cheaper than making physical modifications.

[relaxok]

I'm more bothered by the lack of protected left turn arrows at intersections that need them.  Traffic is so heavy there's no chance to turn left during the green phase, so people wanting to turn run the yellow and collide with oncoming traffic also running the yellow.

I was just thinking about that.

I'm grateful every time I *DO* get an intersection with a protected left arrow, in SF.   The places without them you get ~1 car through per cycle (2 if someone's feeling dangerous)

[Halian]

I hate the intersections that have the left arrow AND the traffic going straight.  It turns red and the other direction does the same.

What's wrong with simultaneous straight and left-turn traffic in the same direction?

[ftballfan]

Sometimes it seems like protected left turns are installed at random. You'll go through three or four intersections with permitted/protected (doghouses) or FYA's, then all of a sudden you hit one with a protected left. I've started to figure out that sight distance issues are probably the reason most protected lefts are installed amongst a sequence of doghouses or FYAs.

There are two of those protected lefts in Ludington, MI (US-10/Meyers Rd and US-10/Brye Rd). Both intersections are home to a big box store (Walmart at Meyers Rd and Meijer at Brye Rd). The US-10/US-31 SB on ramp, US-10/PM Highway, and US-10/Jevaby Rd intersections are FYA. I go through all of those every day on my way to/from work. At least I don't have to turn left at one of those protected left intersections.

[roadfro]

Does the presence of a "Yield on (FYA)" or "Yield on (green ball)" sign imply that one should wait behind the stop line for traffic to clear, or is waiting within the intersection still good? I still haven't figured out if the sign changes anything.

You should always pull into the intersection.

Not necessarily, but generally a good rule.

If opposing traffic is heavy, I pull into the intersection only if there is a car waiting behind me. My logic is that if I pull beyond the stop line and there is no car behind me, I'm most likely out of the vehicle detection zone--if the signal is set to trigger a lagging protected left if turning traffic is still present at the end of the phase, the signal controller won't know I'm still waiting if I've pulled out beyond the detection zone.

[jakeroot]

If opposing traffic is heavy, I pull into the intersection only if there is a car waiting behind me. My logic is that if I pull beyond the stop line and there is no car behind me, I'm most likely out of the vehicle detection zone--if the signal is set to trigger a lagging protected left if turning traffic is still present at the end of the phase, the signal controller won't know I'm still waiting if I've pulled out beyond the detection zone.

Unless I'm mistaken, it shouldn't matter. If the signal skips the lagging turn phase because it doesn't sense anyone, you can still go once oncoming traffic has cleared.

[Perfxion]

Without reading the whole thread, Texas has started turning those turn lanes into Flashing Yellow Lights to yeild to oncoming traffic or to take your turn without waiting the whole time. Only protected green if its at the start of the light cycle and there are enough cars to trip the switch.

[jeffandnicole]

If opposing traffic is heavy, I pull into the intersection only if there is a car waiting behind me. My logic is that if I pull beyond the stop line and there is no car behind me, I'm most likely out of the vehicle detection zone--if the signal is set to trigger a lagging protected left if turning traffic is still present at the end of the phase, the signal controller won't know I'm still waiting if I've pulled out beyond the detection zone.

Unless I'm mistaken, it shouldn't matter. If the signal skips the lagging turn phase because it doesn't sense anyone, you can still go once oncoming traffic has cleared.

This is where the yellow trap was born. 

If the opposing direction gets a lagging turn phase, your direction gets the red light.  In the meantime, the opposing direction still has a green.  Many people mistakenly think that once their light has turned red, the opposing direction's light turned red as well, and will make a turn in front of full-speed traffic.

[tcorlandoinsavannah]

They've started to install flashing yellow left arrows at some lower-volume intersections in Savannah.  Based on the driving skills of most residents and tourists, it will soon be known as "T-bone City".
Personally, I like it; but I've already seen some close calls at an intersection near work.

[vdeane]

This is where the yellow trap was born. 

If the opposing direction gets a lagging turn phase, your direction gets the red light.  In the meantime, the opposing direction still has a green.  Many people mistakenly think that once their light has turned red, the opposing direction's light turned red as well, and will make a turn in front of full-speed traffic.

Generally not a good idea to turn in front of traffic regardless.  Drivers shouldn't rely on whether they think the other side is also red or not but by what traffic is doing.  Even if the other side is red, someone could run the light - especially important as the vast majority of red light violations occur within the first second of the light turning red.

[CapeCodder]

Saint Louis has a gaggle of these. The worst is Kingshighway and Lindell.

[jakeroot]

This is where the yellow trap was born. 

If the opposing direction gets a lagging turn phase, your direction gets the red light.  In the meantime, the opposing direction still has a green.  Many people mistakenly think that once their light has turned red, the opposing direction's light turned red as well, and will make a turn in front of full-speed traffic.

Generally not a good idea to turn in front of traffic regardless.  Drivers shouldn't rely on whether they think the other side is also red or not but by what traffic is doing.  Even if the other side is red, someone could run the light - especially important as the vast majority of red light violations occur within the first second of the light turning red.

I don't turn when the light turns yellow. I turn when traffic has stopped. If my light turns red, and oncoming traffic doesn't stop, my instinct tells me to look in my mirror to see if their light is green. If it is, I wait until it isn't and then complete the turn. I still legally entered the intersection on green, it just got kind of awkward for a second.

[KEK Inc.]

This is where the yellow trap was born. 

If the opposing direction gets a lagging turn phase, your direction gets the red light.  In the meantime, the opposing direction still has a green.  Many people mistakenly think that once their light has turned red, the opposing direction's light turned red as well, and will make a turn in front of full-speed traffic.

Generally not a good idea to turn in front of traffic regardless.  Drivers shouldn't rely on whether they think the other side is also red or not but by what traffic is doing.  Even if the other side is red, someone could run the light - especially important as the vast majority of red light violations occur within the first second of the light turning red.

I don't turn when the light turns yellow. I turn when traffic has stopped. If my light turns red, and oncoming traffic doesn't stop, my instinct tells me to look in my mirror to see if their light is green. If it is, I wait until it isn't and then complete the turn. I still legally entered the intersection on green, it just got kind of awkward for a second.

You should do that regardless, since traffic doesn't always stop on red. 

Yellow traps are still poor traffic design.

[Gnutella]

Here in Georgia, I've sat at intersections with dual left-turn lanes during the wee hours of the morning without the traffic signal even detecting me there. It'd skip the left-turn cycles altogether! And this is with dual lane sensors, which required me to back up about 20 feet and position my truck diagonally across both left-turn lanes in order to jog both sensors and give the hint that somebody's there. When somebody is forced to break the law in order to even go anywhere when there's no traffic, whether it's a failure to stay in one lane or just running a red light, then there's a big problem.

[tradephoric]

Here in Georgia, I've sat at intersections with dual left-turn lanes during the wee hours of the morning without the traffic signal even detecting me there. It'd skip the left-turn cycles altogether! And this is with dual lane sensors, which required me to back up about 20 feet and position my truck diagonally across both left-turn lanes in order to jog both sensors and give the hint that somebody's there. When somebody is forced to break the law in order to even go anywhere when there's no traffic, whether it's a failure to stay in one lane or just running a red light, then there's a big problem.

What type of detection was out there when you got skipped?  It's well documented that video detection technology has trouble detecting vehicles in low-light conditions.  The Indiana Department of Transportation has enacted a moratorium on video detection due to its substandard performance. 

Contact:  James Sturdevant, Traffic Systems Engineer, INDOT Operations Support
E-mail: jsturdevant@indot.state.in.us  Phone: 317-232-5073.

"INDOT has experience with a wide variety of non-invasive detection technologies.  We have found that the only detection technology as accurate and reliable as an induction loop is an induction loop.....

INDOT has enacted a moratorium on the use of video detection due to substandard performance. Rain, snow, fog, wet pavement, headlight glare, sunrise/sunset, wind, lighting changes, shadows, and occlusion from adjacent and crosslanes can all cause detection errors. Use only where induction loops are not practical."

[jakeroot]

Pierce County (where I live) and WSDOT both use video detection. So far, it's only failed me once. A couple weeks ago, similar to above, I was sitting in a dual left turn lane waiting to do a U-turn. Light was sitting red. Three different cars showed up opposite me (to turn towards what would be my right) and each time, it tripped the through light and gave them a green arrow. I, on the other hand, never got a thing. I eventually just went. Yes, it was dark out. And yes, I'm thinking that's what was responsible for my issue. There's a gas station on the opposite side of the intersection from where I was sitting, and I think the ambient light from the station made the opposite side's turn lanes easier to see for the camera.

[roadfro]

The traffic cameras sense a change in contrast in a particularly defined zone on the screen, so it's not just being able to "see" a vehicle or better ambient lighting making detection better. Even if the car is black and sitting on black pavement, the headlights at night should be enough to trip the detection.

That said, there are issues with some detection software and some vendors are better than others... I've never had any issue at video detection signals anywhere in Nevada or California.

[tradephoric]

The traffic cameras sense a change in contrast in a particularly defined zone on the screen, so it's not just being able to "see" a vehicle or better ambient lighting making detection better. Even if the car is black and sitting on black pavement, the headlights at night should be enough to trip the detection.

That said, there are issues with some detection software and some vendors are better than others... I've never had any issue at video detection signals anywhere in Nevada or California.

A number of studies spanning the past 20 years have demonstrated performance issues with video detection technology (whether it be missed calls, false calls, stuck on calls, or dropped calls).  Here's an abstract of a study comparing the "illumination and wind effects on video detection performance at signalized intersections" :

The detection performance of video detection systems at intersections, from three major manufacturers, was evaluated using a side-by-side installation and large datasets. The performance at three stop bar detection zones under two illumination conditions is presented: day with no shadows (cloudy days) and night. In addition, these two conditions and day time with shadows (sunny mornings) are also evaluated under windy conditions. Four measures of performance were used to quantify the errors in the detection: false calls, missed calls, stuck-on calls, and dropped calls. Activation and deactivation times of the detection zones were used to automate the initial calculation of errors, while video images from the intersection were used for their manual verification. Night time results showed an average decrease in false calls for the left-most lane (from about 14% to9%), but an increase for the middle lane (from 1.5% to 23%) and thru-right lane (from 0.8% to 13%). Vehicle headlights reflecting on adjacent zones and the view angle of the cameras were important factors in false calls. Missed calls in night time increased only for one system in one lane (from 0.2% to 26%). Wind increased false calls, mostly in sunny morning conditions (long shadows) between 12% and 17% on average, and reduced stuck-on calls due to the camera oscillation movement. Missed calls increased in day time only, from 0.9% to 2.4%, but it was not possible to identify the exact cause for this increase after a visual inspection of the videos.

There are major swings in accuracy with video detection systems depending on the weather and illumination conditions present.  These are inherent problems that have plagued video detection systems from day one.  Manufacturers have had 20+ years to improve the video detection systems with limited success.  INDOT was so dissatisfied with the operational performance that they placed a moratorium on video detection at signalized intersections.  Are the vendors in Indiana really that much worse than the vendors in Vegas and California? 

[jakeroot]

OT: Is there any detection system that can detect cyclists? I would assume, between the in-ground plate and the camera, the latter would have a higher success rate.

[NE2]

OT: Is there any detection system that can detect cyclists? I would assume, between the in-ground plate and the camera, the latter would have a higher success rate.

I've been successfully detected by both, but I don't think I've tried a camera at night.

[cl94]

OT: Is there any detection system that can detect cyclists? I would assume, between the in-ground plate and the camera, the latter would have a higher success rate.

I've been successfully detected by both, but I don't think I've tried a camera at night.

Bet you haven't tried the metal detectors NYSDOT loved in the late 90s-early 2000s. Unless you're directly over the square (which is less than 1 ft^2 and, by this point, surrounded by a pothole making it dangerous for everyone who can't straddle it), you won't get detected. Flipping nightmare on a bike as you won't ever get detected. At least they moved back to induction loops and started using radar and infrared detectors, but a bunch still remain in the field.

[signalman]

There is a double right turn that I use frequently that does not allow RTOR.  Video detection is used at this intersection.  I often use this intersection around 5 am, so it isn't uncommon for me being the only vehicle intending on turning right.  I almost always want to use the left right turn lane, since I need to use the left lane once I make my right turn.  One morning, however, I used the right lane, since I wanted to make a right turn after the intersection to visit a convenience store.  I found out the hard way that video detection doesn't work as designed in the right lane.  I waited over 5 minutes and never got a green light (normal wait is 2 minutes maximum).  I was getting frustrated and was about to turn right, after looking all over for a cop who might be watching nearby.  Just then another vehicle comes along and stops in the left right turn lane and the signal almost immediately tripped.  I then figured out why I never got a green light.  Ever since then, I've made it a point to use the left lane, even if I want to patronize the aforementioned convenience store.  I will just turn into the left lane and make a quick lane change into the right lane after completing my turn.

[tradephoric]

Here's an example of Forward Looking Infrared (FLIR) detection.  This was a demonstration video posted by FLIR traffic. 

FLIR Thermals help monitor an intersection for incidents as well as optimize the flow of traffic by offering superior vehicle detection! For more information, email us at flirtraffic@gmail.com.

There is a stuck on call observed at the very start of the video (top-right video, left turn lane).  That's not superior vehicle detection when you can spot a fault within the first second of the video.  I'm a bit surprised the company would think this is a good demonstration video to post onto youtube. 

[jakeroot]

Here's an example of Forward Looking Infrared (FLIR) detection.  This was a demonstration video posted by FLIR traffic. 

FLIR Thermals help monitor an intersection for incidents as well as optimize the flow of traffic by offering superior vehicle detection! For more information, email us at flirtraffic@gmail.com.

There is a stuck on call observed at the very start of the video (top-right video, left turn lane).  That's not superior vehicle detection when you can spot a fault within the first second of the video.  I'm a bit surprised the company would think this is a good demonstration video to post onto youtube.

Was the video aimed at other traffic engineers or the general public? I assume the former. But more to the point, what the hell is a "stuck on call"?

[tradephoric]

Was the video aimed at other traffic engineers or the general public? I assume the former. But more to the point, what the hell is a "stuck on call"?

A "stuck-on call"  is when detection remains active even after vehicles depart from the detection zone.  From my experience, FLIR cameras experience a lot of random stuck-on calls.