Why do Louisville Traffic lights have a different yellow visor.

[Amtrakprod]

I've been wondering this for a while, Anyone know?

[Amtrakprod]

Heres what a picture looks like:
Screen Shot 2018-05-26 at 6.18.00 PM by Petru Sofio, on Flickr

[Big John]

It is all of Kentucky that does that.  I think a study was done there that came to a conclusion that traffic operates better that way, but I am unsure.

[kalvado]

Not sure if that is related, but when first LED traffic lights were competing with incandescent,  energy and maintenance costs were estimated to justify the conversion. A common conclusion was that green and red have to become LED from $$ perspective -  but short yellow cycle does not use enough energy to justify cost of LED  conversion, and lamp lifetime is long due to short cycle.
looking at the picture, this yellow may actually be incandescent - and that could be the difference. 

[jeffandnicole]

Not sure if that is related, but when first LED traffic lights were competing with incandescent,  energy and maintenance costs were estimated to justify the conversion. A common conclusion was that green and red have to become LED from $$ perspective -  but short yellow cycle does not use enough energy to justify cost of LED  conversion, and lamp lifetime is long due to short cycle.
looking at the picture, this yellow may actually be incandescent - and that could be the difference. 

But no other state consistently used 2 different visors because of this.

[hbelkins]

I don't think the yellows in Kentucky are still incandescent. But I have no idea why the visor for the yellow lights in Kentucky is different.

[Brandon]

I don't think the yellows in Kentucky are still incandescent. But I have no idea why the visor for the yellow lights in Kentucky is different.

My best guess, and this is purely conjecture, is that the yellow might be washed out in the sun compared to the red and green due, obviously, to its color.  For some odd reason, here in Illinois, IDOT District 3, Kendall County, and Kane County are using cutaways for the red signals and tunnel visors for everything else.  That, I suspect is to help clear snow away from the reds.

[thenetwork]

The same kind of visor setup was prevalent in Akron, Ohio since at least the 70s.  Back then most of their traffic signals were painted dark green or black (they are now the traditional yellow color).  I don't think the odd yellow-lensed visor has anything to do with the color of the traffic light in general.

My guess is that the tunnel visor holds more of the yellow light in, and thus makes it look brighter than the green or red lights with cutout visors, which in turn may attract more attention to the human eye. 

[US 89]

My guess is that the tunnel visor holds more of the yellow light in, and thus makes it look brighter than the green or red lights with cutout visors, which in turn may attract more attention to the human eye.

But if tunnel visors make the lights more visible, then why don't we use them on all signals?

[NoGoodNamesAvailable]

But if tunnel visors make the lights more visible, then why don't we use them on all signals?

I believe it's because snow can accumulate on the bottom of tunnel visors.

[kalvado]

My guess is that the tunnel visor holds more of the yellow light in, and thus makes it look brighter than the green or red lights with cutout visors, which in turn may attract more attention to the human eye.

But if tunnel visors make the lights more visible, then why don't we use them on all signals?

Again to point out possible difference between incandescent and LEDs:
Incandescent lights release enough heat to prevent snow accumulation..

[Beltway]

Because they are "special"? 

I know that some posters here don't like Bat City.

[hotdogPi]

Because they are "special"? 

I know that some posters here don't like Bat City.

What do you mean by "Bat City"? A quick Google search doesn't give a clear answer as to which city it is but seems to imply that it's Austin, not Louisville.

[Beltway]

Because they are "special"? 
I know that some posters here don't like Bat City.

What do you mean by "Bat City"? A quick Google search doesn't give a clear answer as to which city it is but seems to imply that it's Austin, not Louisville.

I'm sure you have heard of the Louisville Slugger.

[hbelkins]

Because they are "special"? 
I know that some posters here don't like Bat City.

What do you mean by "Bat City"? A quick Google search doesn't give a clear answer as to which city it is but seems to imply that it's Austin, not Louisville.

I'm sure you have heard of the Louisville Slugger.

He is, of course, referring to me and my general dislike for Louisville.

But this isn't strictly a River City phenomenon. It happens all over Kentucky.

[Beltway]

Because they are "special"? 
I know that some posters here don't like Bat City.

What do you mean by "Bat City"? A quick Google search doesn't give a clear answer as to which city it is but seems to imply that it's Austin, not Louisville.

I'm sure you have heard of the Louisville Slugger.

He is, of course, referring to me and my general dislike for Louisville.
But this isn't strictly a River City phenomenon. It happens all over Kentucky.

As I am aware.

But they do make a mean bat, don't they?

[jeffandnicole]

But if tunnel visors make the lights more visible, then why don't we use them on all signals?

I believe it's because snow can accumulate on the bottom of tunnel visors.

Doesn't prevent the northern States from using them.

I'd be surprised if that was the real reason, being snow isn't exactly a long winter issue down there.

[freebrickproductions]

From what I understand, this practice was much more common across America years ago, especially back in the days of just a single 4-way signal hanging above each intersection with no pedestrian signals. The theory was that the yellow light was so bright that it'd shine into the windows of neighboring houses, so a tunnel visor or full circle visor would be placed on it to limit the side-splash of the yellow light. However, as this was in the days of one signal per direction with no ped signals, the red and green had cut-away visors on them to make it easier for pedestrians to see if the light facing them was green or not. As time went on and signal standards and practices were changed, most places have dropped the use of this funky style of visor arrangement, though Kentucky as a whole (for the most part) continues to use this odd-looking arrangement on their signals. However, I have also seen evidence of it being used in Ohio (as mentioned upthread), Alabama, and Michigan as well.

Also, IIRC, Kentucky also puts tunnel visors on all arrow indications, so the cutaways are typically only used on red and green balls.

[Amtrakprod]

Also, IIRC, Kentucky also puts tunnel visors on all arrow indications, so the cutaways are typically only used on red and green balls.

That I think is wrong according to this g maps shot, but I know New York does that:


iPhone

[lepidopteran]

IIRC, they were doing this before the widespread use of LED signals.

[freebrickproductions]

Also, IIRC, Kentucky also puts tunnel visors on all arrow indications, so the cutaways are typically only used on red and green balls.

That I think is wrong according to this g maps shot, but I know New York does that:


iPhone

IIRC, I remember seeing doghouses around Kentucky with tunnels on the arrows, so it could be one of those regional things. Though I also do recall the inline-4 signals only having it on the yellows as well...

IIRC, they were doing this before the widespread use of LED signals.

As I said earlier, many places across America were doing this back in the 40s and 50s (and probably into the 60s).

[CardInLex]

The reason is quite simple actually. The yellows are shielded this way to prevent drivers on the cross road from seeing the signal turn yellow and start to move before they receive a green. Also, the cutaways (on red and green) help if a signal bulb is out. Drivers approaching an intersection that (if for some reason) has both signals burned out, can look at the cross traffic signal and see what the color the cross traffic has and know to do the opposite.

Both of these reasons don't apply much today since signals are normally mounted on separate spans and thus much more visible to all directions, but a lot of signals in KY were originally diagonal spans which would have an cluster of signals for every direction on them (some of the Old Louisville) neighborhood still has this configuration.

Example:
https://www.google.com/maps/@38.2286731,-85.7580667,3a,60y,90t/data=!3m6!1e1!3m4!1sUxnb-DQSKrz9MgSEqrvLOQ!2e0!7i13312!8i6656
EDIT: This example actually features incorrect visors on one of the indications.

Here is an example that is correct:
https://www.google.com/maps/@38.237431,-85.7582474,3a,27.2y,186.55h,88.47t/data=!3m7!1e1!3m5!1sbLCo7MTcPxPC1bKetth0Rw!2e0!5s20170201T000000!7i13312!8i6656

[hbelkins]

There are a few of those old four-way signals left around the state. Downtown Carlisle has a few.