Proposal to add fourth traffic light help transition to autonomous vehicles

[Dustin DeWinn]

There are many many articles about this that appeared over the past couple days

here's one

https://www.popularmechanics.com/technology/infrastructure/a42804174/fourth-color-traffic-light-white/

[Max Rockatansky]

Huge problem, we don't have autonomous vehicles and we aren't likely to get "real"  iterations soon. 

[Rothman]

White means to just follow the car in front of them?  Why not just keep it green?

Red-green colorblind people would have problems with the white light, since green lights are already diluted in their vision.  A magenta shade of purple would work better, if we really must do this, as purple is suggested in the article.

[Dustin DeWinn]

I cannot imagine the cost of replacing every single traffic light chassis in the country or even in one state and having to program the timing of it only to have this be a temporary stopgap

[Rothman]

I cannot imagine the cost of replacing every single traffic light chassis in the country or even in one state and having to program the timing of it only to have this be a temporary stopgap

Yep.  Signals right now are extremely expensive, when in years of yore they were considered cheap.  In central NY, signal replacements for one typical intersection are now maxing out at $300,000.  Signal replacement projects were set up to handle multiple locations, so those projects are increasing in price considerably.  $1m projects are now costing $3m...

[Big John]

White means you can walk across the intersection.

[hotdogPi]

White means you can walk across the intersection.

Unless it's an emergency signal.

[plain]

White is also used for LRT and BRT systems.

https://maps.app.goo.gl/LMpW8rUXhWnFnYuG9

[Scott5114]

I cannot imagine the cost of replacing every single traffic light chassis in the country or even in one state and having to program the timing of it only to have this be a temporary stopgap

Yep.  Signals right now are extremely expensive, when in years of yore they were considered cheap.  In central NY, signal replacements for one typical intersection are now maxing out at $300,000.  Signal replacement projects were set up to handle multiple locations, so those projects are increasing in price considerably.  $1m projects are now costing $3m...

What's driving the cost increase? Aren't signal heads these days basically just plastic? And LEDs aren't that expensive... Is it just higher cost of labor and chips?

[interstatefan990]

For the dawning age of the self-driving car, transportation engineers from North Carolina State University are proposing the addition of a fourth "white light"  whose function would be to alert humans to simply "follow the car in front of them."

Sorry but what? We've taught drivers for decades to never trust that another driver will do a certain thing or take a certain action, and now we're supposed to just drive straight through an intersection because the oh-so-smart autonomous car in front of us is?

[Dirt Roads]

White is also used for LRT and BRT systems.

https://maps.app.goo.gl/LMpW8rUXhWnFnYuG9

Lunar white is also used in railroading, but means "Call-on Signal".  This has a similar connotation as to the use of a white aspect with autonomous vehicles.  While the "Call-on Signal" gives an aspect that indicates "Proceed, prepared to stop in 1/2 sight distance" the actual use indicates to train crews to "follow the leader".  The intention here may be similar as well, since the practical use of the "Call-on Signal" is to pull a train through to the other side of the [intersection] (ergo, interlocking) rather than stopping at the signal and blocking the route of next train.

I have a concern about the use of a white aspect on traffic signals for this purpose.  Human drivers will soon learn that whenever one driver gets a "Follow-the-Leader" aspect, then everyone else can do the same (even if the traffic signal goes into a different phase and turns yellow, then red).  It is one thing that in New Jersey, six to eight cars will run the light after it turns red.  It is another thing when 15 to 20 cars decide to "Follow-the-Leader" to hop over to the next junction.  This is a sure-fire way to get into a gridlock situation somewhere down the line.

[hotdogPi]

Traffic lights wouldn't be needed at all if all cars were self driving. There would just be 2 continous perpendicular streams of cars essentially passing between each other as they approach the intersection at high speed. A supercomputer network would control the precise speeds and directions of the cars so they would all never hit each other (although they may come within a few millimeters of each other).

And pedestrians?

[formulanone]

The traffic lights, they turn blue tomorrow.

[Rothman]

I cannot imagine the cost of replacing every single traffic light chassis in the country or even in one state and having to program the timing of it only to have this be a temporary stopgap

Yep.  Signals right now are extremely expensive, when in years of yore they were considered cheap.  In central NY, signal replacements for one typical intersection are now maxing out at $300,000.  Signal replacement projects were set up to handle multiple locations, so those projects are increasing in price considerably.  $1m projects are now costing $3m...

What's driving the cost increase? Aren't signal heads these days basically just plastic? And LEDs aren't that expensive... Is it just higher cost of labor and chips?

Nope.  I am talking complete reconstruction, so including replacing poles, if necessary.

So, yes, materials and labor are rising in cost, especially as more funding is provided at the state and federal levels and contractors in rural and small urban areas are overwhelmed by the increase either in number of lettings or in contract size (we can afford the big project now!).  These are the main variables.

However, policy changes may also be a factor.  NYSDOT, with every paving job that requires ripping up loops, is replacing loops with video detection.  That's an increased cost as those systems are installed as well.  Secondary to material cost increases, but a big number two.

[Hobart]

I will respond here like I did on Facebook:

Extend the yellow light by a second, extend the all-red phase by a second, and change the definition for a yellow light to "go if you can cross the stop bar before the red light" to encourage more people getting into the intersection... which would entail following the car in front of them!

What do you do if you're the first car, and the light is white anyways? There would inevitably be some difficulty detecting which car is self driving; yeah there can be some kind of transponder, but stuff breaks all of the time.

This would also require a standard to be established for cars to communicate with signal controllers... which standard will win? Will current autonomous vehicles become useless?

Not to mention, there are a fair number of issues with autonomous driving in the first place, before you even touch a signal head. I will not elaborate here, because that horse is already dead and beaten!

[SectorZ]

A Gizmodo writer from Portland overlooking the safety aspects regarding cyclists and pedestrians.

Kind of sad when I need these people to be useful idiots for the likes of me and they can't be bothered.

[JREwing78]

Extend the yellow light by a second, extend the all-red phase by a second, and change the definition for a yellow light to "go if you can cross the stop bar before the red light" to encourage more people getting into the intersection... which would entail following the car in front of them!

I'm with you there. Human drivers have a hard enough time dealing with the three signal colors we've already got, let alone with recent additions like the flashing yellow arrow for permissive left turns.

[kalvado]

Add infrared diodes to yellow as a second color if that is for computer only. No confusion for humans...

[kalvado]

Huge problem, we don't have autonomous vehicles and we aren't likely to get "real"  iterations soon.

Actually we do. Not in the streets, but there are mines running with driverless trucks. They make a good point that some facilities, like cargo terminals, may get more of those.

I still don't understand what autonomous vehicles should be doing here if that cannot be relayed to a regular RYG head

[Henry]

I say there should be a separate signal for autonomous vehicles that will correspond to the traditional RYG phase. If I were an engineer for FHWA, I'd come up with the following proposals:

STOP: Red octagon
CAUTION: Yellow triangle indicating travel direction (up for straight through, and sideways for left/right turns)
GO: Green triangle, also indicating travel direction

[GaryV]

I say there should be a separate signal for autonomous vehicles that will correspond to the traditional RYG phase.

What would be the benefit of that? Why would autonomous vehicles have separate traffic light phases?

I also don't understand the reasoning for a white light. "Just keep following the vehicle ahead of you." What if I don't want to go that way?

[kalvado]

I say there should be a separate signal for autonomous vehicles that will correspond to the traditional RYG phase. If I were an engineer for FHWA, I'd come up with the following proposals:

STOP: Red octagon
CAUTION: Yellow triangle indicating travel direction (up for straight through, and sideways for left/right turns)
GO: Green triangle, also indicating travel direction

It is a totally different concept.
What they say is white should be a permissive phase where connected vehicles do communicate and use smaller gaps in traffic. Sort of yield in high-tech version with every automatic car being willing to cooperate.  They assume automatic cars can slow down and  accelerate to optimize gaps in the stream to let cross and left turns through (unlike humans who are always willing to accelerate and close the gap)
paper is available: https://www.newswise.com/pdf_docs/167577509263217_Hajbabaie%20white%20phase%20intersection%202023%20FINAL.pdf
Although there are too many formulas from my perspective to make things believable.

UPD: OK, to clarify: concept is that driverless cars can negotiate a very short, maybe 2 second "red" period during white phase to allow 1 car from a low traffic side road to squeeze through. That is instead of minimum 10 second  for traditional red (including both yellows) 

[Dirt Roads]

What they say is white should be a permissive phase where connected vehicles do communicate and use smaller gaps in traffic.

"Merge-at-speed" is a common function in modern Personal Rapid Transit (PRT) systems that utilize much of the same technology as [autonomous cars].  These PRT system do have a centralized [master control system] that is similar to Automated Transit Supervision (ATS) in other forms of rail transit and automated guideway systems.  The ATS for a PRT system generally assigns vehicle "slots" that operate around the mainline; some of the "slots" are occupied by vehicles and some the "slots" are virtual and unoccupied.  The typical PRT philosophy involves "off-line stations" where the vehicles pull off the mainline to discharge passenger, pull forward to receive passengers at a different berth and then accelerate to the merge point to access a "slot".  In cases where no slot is available, the ATS will slow down some vehicles to create a new slot in advance of the merging vehicle.  This same approach could be used at perpendicular intersections.  Which leads us to...

Traffic lights wouldn't be needed at all if all cars were self driving. There would just be 2 continous perpendicular streams of cars essentially passing between each other as they approach the intersection at high speed. A supercomputer network would control the precise speeds and directions of the cars so they would all never hit each other (although they may come within a few millimeters of each other).

Signals are still needed at all intersections and merge points.  One of the most difficult issues we deal with in the world of [driverless trains and other similar thingys] is that the vehicles can (and do) lose their automation, and even worse, lose communication with the centralized [master control system].  Dealing with all of the crazy issues related to what the industry calls "Non-Communicating Trains" (NCTs) is a technological and philosophical world unto itself.  All of which requires wayside signals to deal with the safety issues related to how a manually-driven vehicle can avoid side-swipes in the middle of a sea of autonomous vehicles. 

I don't know the folks at N.C. State that are recommending the fourth white aspect, but the "Follow-the-Leader" approach appears to fit very well into the "Merge-at-speed" philosophy used in modern PRT systems.

[kalvado]

What they say is white should be a permissive phase where connected vehicles do communicate and use smaller gaps in traffic.

"Merge-at-speed" is a common function in modern Personal Rapid Transit (PRT) systems that utilize much of the same technology as [autonomous cars].  These PRT system do have a centralized [master control system] that is similar to Automated Transit Supervision (ATS) in other forms of rail transit and automated guideway systems.  The ATS for a PRT system generally assigns vehicle "slots" that operate around the mainline; some of the "slots" are occupied by vehicles and some the "slots" are virtual and unoccupied.  The typical PRT philosophy involves "off-line stations" where the vehicles pull off the mainline to discharge passenger, pull forward to receive passengers at a different berth and then accelerate to the merge point to access a "slot".  In cases where no slot is available, the ATS will slow down some vehicles to create a new slot in advance of the merging vehicle.  This same approach could be used at perpendicular intersections.  Which leads us to...

Traffic lights wouldn't be needed at all if all cars were self driving. There would just be 2 continous perpendicular streams of cars essentially passing between each other as they approach the intersection at high speed. A supercomputer network would control the precise speeds and directions of the cars so they would all never hit each other (although they may come within a few millimeters of each other).

Signals are still needed at all intersections and merge points.  One of the most difficult issues we deal with in the world of [driverless trains and other similar thingys] is that the vehicles can (and do) lose their automation, and even worse, lose communication with the centralized [master control system].  Dealing with all of the crazy issues related to what the industry calls "Non-Communicating Trains" (NCTs) is a technological and philosophical world unto itself.  All of which requires wayside signals to deal with the safety issues related to how a manually-driven vehicle can avoid side-swipes in the middle of a sea of autonomous vehicles. 

I don't know the folks at N.C. State that are recommending the fourth white aspect, but the "Follow-the-Leader" approach appears to fit very well into the "Merge-at-speed" philosophy used in modern PRT systems.

Well, and how well that functions? I believe FAA awarded contract for a similar free-flow air traffic control system... I am not sure, 2005-2010 range? it is 2023
Quick google look up says 2008 for the  NextGen ATC contract, 2030 current first trial date - lets make it 2050 to be realistic. That is with pilots at controls and communicating with dispatch at all times as a hot backup....

[Dirt Roads]

I don't know the folks at N.C. State that are recommending the fourth white aspect, but the "Follow-the-Leader" approach appears to fit very well into the "Merge-at-speed" philosophy used in modern PRT systems.

Well, and how well that functions? I believe FAA awarded contract for a similar free-flow air traffic control system... I am not sure, 2005-2010 range? it is 2023
Quick google look up says 2008 for the  NextGen ATC contract, 2030 current first trial date - lets make it 2050 to be realistic. That is with pilots at controls and communicating with dispatch at all times as a hot backup....

Most of the PRT systems (and AGT systems with similar "slot-based" centralized [master control systems]) also have hot backup (and we always required such on the ones I worked on).  But your comment has a valid point.  Railway traffic control is one-dimensional; highway traffic control is two-dimensional; and air traffic control is three-dimensional.  The "follow the leader" principle only works if all vehicles function well at the same speed *and* the terminal points operate nearly congestion-free.  Which leads to an obvious conclusion...

An efficient autonomous car network will need all of the cars to make quick berthings (passenger drop-offs/pick-ups) in the urban core and then get sent back out (ergo, empty cars).

Oh, oh, oh... And I should mention that the network needs to have enough "lanes" (or parallel "routes") to support the peak demand at the minimum operable headway.  Someone out there is still very angry at me for calculating that a certain proposed PRT system would need to be 12 lanes wide.  On the other hand, one of my colleagues was upset that I used a minimum operable headway of 20 seconds, instead of the industry standard of 45 seconds.  Given the variation of acceleration/deceleration capabilities in such a big fleet, he was probably more realistic than I was.