Safety Feature For Pedestrians Has Undesired Consequence | Hacker News Reader

Safety Feature For Pedestrians Has Undesired Consequence

npr.org

76 pointseroo93 comments

I sit above a pretty busy intersection and get to witness the madness and regular accidents of rush hour traffic heading out of downtown on a daily basis.

I think simply shimming an extra second or of intersection clearing time between transitions would go long way towards addressing the apparent dangers of light timing.

Activating traffic signals and pedestrian signals simultaneously results in drivers who try to 'beat' the pedestrians off the curb.

Activating perpendicular traffic signals too close traffic/pedestrian signals puts the cross-traffic in danger of being hit by the people trying to time the light.

Add a second or two, end up with <5 fewer light transitions per hour.

Though, on a related note, what I see cause more accidents and general bullshit than timing lights is the ridiculous amount of cellphone use that happens in motion and particularly at intersections.

Every day I see someone stop at the red light below me and immediately start fiddling with their phone, as the light turns green and the fiddler proceeds to hit the gas irrespective of what is happening in the road directly in front of them - pedestrians, gridlock, presidential motorcade only to run into something or panic stop seconds later if they're lucky.

At first this seemed inexplicable..."Can't these people see?"

Upon thinking about it, I'm guessing they actually can't or more accurately don't see. That the fraction of a second they have to hit the gas before getting a chorus of horns or a rear-ending is simply too short to take in even major changes in the scene in front of them.

Self-driving cars can't come soon enough.

If you live in a culture where disobeying traffic signals is common (especially non-drivers...say in China...), you observe that people become much more cautious about light transitions. I always cringe driving back in the states and just going as soon as a light turns green.

A kid rushing after a ball into a crowded street in the US is probably dead meat. In China, they have a much better chance of surviving because drivers are used to that crap (likewise for pedestrians and crazy drivers). Though I would venture that the fatality rate is still much higher China (I've personally seen people get hit and killed).

I've never seen an intersection that didn't have some amount of time where it was red in all directions during a light change. I can't find references to back it up right now but I'm pretty sure that in cases where this period is extended you end up with drivers adapting and driving through a stale yellow that they would have previously stopped for.

In most of California it seems that the next set of lights turns green as soon as the previous set turns red. In Ontario, Canada I believe there is a 2 or 3 second delay. I don't think that I've noticed any difference in the behavior of people around yellow lights except for the fact that in California it seems people are more willing to run red lights, and the intersection is almost never clear when the next green light happens (unless, of course, traffic is sparse). In Ontario, Canada the intersection is almost always clear when the next green light happens.

In the UK a lot of intersections change light at the same time(so as soon as one side goes to red, the other side changes to yellow already).

Add a second or two, end up with <5 fewer light transitions per hour.

Perhaps this is backwards? If the problems occur mostly at transitions, shouldn't we try to minimize transitions with really long lights? Of course at some point there isn't enough room on the block to accommodate stopped traffic...

The point here isn't to have more transitions, but rather to put a delay between a yellow going red and a red going green.

People often treat yellow lights as 'Better hurry up!' and the worst of those people will end up in the intersection when the light turns red; if, at the same time, the other light goes green, impatient people will rush the light and accidents (or near misses) can occur. A driver who rushes and then slams on his brakes when he realizes that someone was still in the intersection can be hit by the person behind him who expected him to go, but didn't expect him to stop.

Extremely long lights will make things worse by increasing driver frustration and eliminating the feasibility of left-turns when an intersection doesn't have an advance left turn. In many downtown areas (of the ones which I've been to), there are no (or few) advance left turns; this means that, typically, you will wait at a red light, then wait at a green light, then turn left on the yellow light. If they're on top of things and you've advanced into the intersection, the person behind you could also manage a left turn.

Longer lights means fewer yellows, which means fewer left turns, which backs up traffic even worse.

I still think self driving cars are the wrong solution to problems that exist.

That's a bit like suggesting that autopilots and automatic landing systems are the wrong solution to reducing air accidents. The only difference is that automatic flight systems in aircraft were introduced in the past and self-driving cars will (presumably) be introduced in the future, but the validity of the approach to the problem is basically the same.

No, my thinking goes along the lines of society wanting/needing to use less cars not more. hence I would be more for mass transit type solutions rather than packing more cars onto the road more (space) efficiently.

It wasn't directly related to traffic accidents in the article, but to what the parent comment said at the end.

Well yes, using cars for urban transport is a bad habit that we should never have got into, and we should now be trying to get out of. But it's logistically and politically impossible to get rid of all cars overnight. There are a number of things we can do to cut down on car usage. Self-driving is something we can do to cut down on the fatality rate per car. Each of these is a partial solution. Partial solutions are complementary, not exclusive.

But self driving cars are a great way to cut down on the number of vehicles on the road via very cheap, highly utilised automated taxis. Vehicles should last a lot longer too because the autopilots would make fewer mistakes such as over-gunning engines, stalling, braking late and terrors more sharply, etc. they could enable huge efficiency savings.

> Self-driving cars can't come soon enough.

This is surprisingly common: people's behaviour around technology is awful, so the solution is more technology! As much as I agree that taking idiot humans out of the decision-making process is a good idea, I wonder what unintended side effects self-driving cars will have.

Also, it's not so difficult to not use your phone at a light, and in many jurisdictions, it is illegal to use a phone or other electronic device (which is not a driving aid, e.g. navigation systems) while in care and control of a vehicle. My wife, for example, refuses to even look at her phone while driving, even if stopped at a light; extremely frustrating for me when I'm trying to get her to pick me up somewhere, but easily defensible when you hear stories like this.

In the end, all of these stories seem to come down to selfishness, ignorance, and carelessness. If people were more aware of the world around them, then these things would be significantly less common. I feel as though technology isn't going to fix that until we've basically eliminated humans entirely from all decision making.

In the trade off between property dammage and pedestrian deaths I am generally going to side with pedestrians.

It is an interesting scenario that they play out in Toronto. However, this is a programmatic feature built into the traffic systems - and in the current location I live in completely different.

Here the countdown hits zero well before the lights shift to yellow and finally red. Perhaps Toronto needs to readjust if there is a high number of rear-ends occurring due to drivers going off of the pedestrian control devices instead of vehicle control devices.

Good point. Here for some reason the pedestrian light is 15 second even if the traffic is going to be flowing in that direction for 45 sec. You can hit the button and it'll start counting down again.

My experience is that the light changes to yellow as the countdown reaches zero.

Here in Phoenix most work this way, but when a road crosses central avenue the walk counter hits 0 and then there is about a 10 second delay before the traffic lights change.

The problem is, people have realized this. So peds continue to begin crossing as the counter gets low (central has a lot of ped crossing because the light rail runs down the middle of the road).

They really ought to reverse that. Make the light shorter for cars and drivers can no longer use the countdown clocks as a signal. They'd have to actually look at their own light. Combine that with starting the pedestrians early and you make it much harder for drivers to be jerks.

I've seen both. On wide multilane roads I've seen the coundown hit zero and the "don't walk" signal come on before the traffic light changes to yellow. On narrower crossings the yellow tends to appear as the counter hits zero or very shortly after.

That's similar to what I've seen in the NY suburbs; I've noticed that the counter hitting zero is when the traffic light goes yellow.

It reduces the number of pedestrians who get hit, and asshole drivers who think they can speed though intersections are getting into accidents.

I don't see the issue.

It has been shown that accidents can occasionally hurt innocent people.

Who do you think the asshole drivers run into? According to the article, drivers who are just trying to be safe by not risking it and slowing down get hit by drivers behind them who speed up.

...drivers who are just trying to be safe...

If their idea of safety is paying attention to pedestrian signals rather than automotive signals, we'd rather they not bother.

Who said anything about "rather than"? What kind of a signal do you expect someone about to rear-end you to give?

They should be looking at the signal that consists of a red lamp above a yellow lamp above a green lamp. While the green lamp is lit, they should keep driving and not slam on the brakes just because the little man in the crosswalk started blinking.

Yes I know that rear-enders are at fault even when the rear-ended did something stupid. In fact many driving accidents can be attributed to the stupidity of multiple parties, and the accidents described above can also be so attributed.

The driver behind them should be watching the car in front of them and be following at a safe distance. I don't see why you should run into the back of someone if they slow down for an intersection with 1-2 seconds left on the timer and they're at a questionable distance about whether they'll make the light.

It's as if you didn't even read the second paragraph, in which I also blamed rear-enders for rear-ending!

If the light is green, there's nothing "questionable". Either one will make the light, or one will have time to slow once it actually turns yellow. If, instead, one does something surprising and irrational, misfortune may result. In this scenario, as in many accident scenarios, both parties have driven poorly.

Yes, I hate those reckless idiots stopping at red lights, too.

I have often seen pedestrian signals where the countdown ends when the red light turns on (so the countdown is still going during the yellow). My reading of the article was thus that the rear-enders are choosing to run more yellow lights, not that the rear-ended are choosing to stop when it's still green. In that case, it's the rear-enders who are paying attention to pedestrian signals and changing their driving as a result, and they're hitting people who are stopping as they approach a yellow in the normal manner.

The article claims that it reduced pedestrian injuries (accidents?), but the asshole drivers run into the cars in front of them, the ones that are stopping for the intersection.

I see your point but I'd happily trade an increase in vehicle-vehicle collisions for a decrease in vehicle-pedestrian collisions. Vehicles have all kinds of safety features that are designed to handle this sort of thing. Pedestrians don't.

This just means both are at fault. The driver in front for not being aware there's an asshole behind him; and the driver behind for being an asshole.

Downvoted I see - funny thing is how legal liability is irrelevant when your car has been pushed into an intersection resulting in your death.

You have responsibility to be aware at all times - even if it's not something you're legally responsible for, when you're in the presence of people driving multiple tons of steel at varying rates of speed, it'd be foolish to believe "but it was his fault" will prevent you from bleeding to death.

Having been hit from behind before, you're almost never at fault when you're hit from behind.

Furthermore, there is sometimes literally nothing you can do. You are not always in control, and you're going to get hit, no matter how "aware" of your surroundings you are.

Vehicle collisions are more survivable than pedestrian collisions; if we're trading one for the other, it seems like a net win for safety.

Even if we don't get fully self-driven cars soon, I really hope we get autopilot to take over for timing left turns and yellow lights, entering a highway, avoiding pedestrians, and maybe all parking.

Sure, many drivers handle that all fine most of the time, but each one seems like a potential point of failure that would benefit from a little more standardization.

EDIT: Or traffic robots that direct instructions to proceed or stop to each specific driver. Seems like we have better options than a colored indicator involving a lot of judgment calls based on conflicting interests.

I'm having trouble understanding this article. If the count down timers show pedestrians the amount of time they have to cross the road (as they do here in London) why would the driver be watching this and think they only have a few seconds until the light goes red and they can't get through the intersection. Surely, the opposite is the case?

I can see that you could potentially form a similar explanation around that scenario too but it doesn't seem as convincing.

I'm assuming this has something to do with being able to turn through a red light, which is illegal in London.

But yeah. I had trouble understanding the issue at all, as you note London has them, I've never noticed any issue at all - if anything, it gets the peds out of the road more timely...

Indeed, in England pedestrians never cross when a vehicle has a green light over the path they are going to cross. I.e. completely separate pedestrian phases.

In the US, the walk lights go 'green' at the same time as traffic parallel to the crosswalk gets a green light, in a shared phase. So if the timer is getting close to zero, it means the vehicles are about to go to a red light, and the opposite direction is about to get the green light.

I'm a bit unsure exactly what it is you are describing. Pretty much all the crossings I use regularly in London follows an at least very similar pattern to what I'm used to seeing in the US when visiting, with traffic parallel to the crossing getting green at the same time as the pedestrian crossing in question

In fact, here's a discussion in the UK Parliament in 2004 where it was proposed to restrict the use of all-red phases in low traffic junctions, and where the person proposing the change saw it as necessary to describe why this was even an issue:

http://www.publications.parliament.uk/pa/cm200304/cmstand/a/...

"Mr. Redwood: Until a few years ago, no one would have understood why new clause 5 would be necessary. All traffic lights that motorists or cyclists encountered on our highways had a simple form of operation which meant that there was always one free route across the junction showing green. In the normal four-way junction where two roads intersected, one road had priority for one phase and the other road had the alternate priority. There could be more complicated variations at larger junctions, but there was always a green phase for vehicles on one part of the junction"

[The proposed clause 5: 'No authority shall be entitled to install or operate traffic signals with all red phases at road junctions where there is no hazard other than traffic.']

You may be right that no vehicles will have green light to cross the pedestrian crossing while pedestrians have a green light, though I'm not 100% sure that's true either - I seem to remember crossings in London at least where turning traffic will have green at the same time as pedestrians, but I don't drive so maybe that's just me as an impatient pedestrian misremembering, as I'll regularly cross on red.

I've never seen or heard of that in the UK: if the green man shows, no vehicle can cross the path. It's quite common for traffic to be moving while some part of the crossing is green, but they wouldn't be allowed to use that lane. Indeed, pedestrians will regularly cross at red man - that's allowed, and people know they need to look out in all directions.

All-red phases are a slightly different issue, and indeed, not all crossings have them

I think the confusion here is that in the UK there is a separate phase for drivers turning left into the junction, whereas in the U.S. drivers can turn right across the path of crossing pedestrians. Obviously the UK system is a lot safer.

As ealexhudson says here: https://news.ycombinator.com/item?id=7975422 , the difference is that in the UK, when you have a 'green man', there is a guarantee that traffic are not permitted to use any piece of road you are crossing.

I was describing the crossroads situation where all vehicles are allowed to travel in any direction when they have a green light (no filter light/lanes), as this is the most commonly occurring situation in towns in the US I think. Not including states where there is a propensity for 'no left turn' intersections.

In the US, this would mean two phases, with each one being a shared pedestrian and vehicle phase, pedestrians crossing in parallel to traffic. In the UK this would be three phases, two traffic and one dedicated pedestrian phase.

I personally prefer the UK system, as in the US as a pedestrian you are at the whim of drivers paying attention to pedestrian traffic, and even if they don't hit you they may well start turning the corner to pressure you to hurry up.

A crosswalk that is parallel to you (i.e., pedestrians traveling in the same direction across the intersection as the drivers) will have a "walk" signal that is synched with the traffic light. In this case, a green light would be analogous to "walk" and a yellow light would be analogous to "3..2..1..".

It is likely that once the cross walk reaches zero, a yellow light will appear on the traffic signal. Anyone reading the walk signal in front of them will have an early warning about the traffic light and may try to speed up to get through.

If you're a block away from the light and you see a "4", what do you do?

The essential piece of information missing from the article, because it's common in the US, is that pedestrians usually get green at the same time as traffic in parallel with them. In Europe it's a more common pattern that all pedestrians walk at an interval when all traffic is stopped and this cheat would indeed not work there.

Not once have I seen this anywhere in Europe. I'm sure you're talking from experience and it's a thing, but it seems to vary from place to place. It sounds a bit inefficient.

Indeed, it is less efficient when cars have to stop for pedestrians and not drive through them.

I don't think it's that common - I've only seen it a couple of places, but it happens. Most places in Europe I've been, there's car traffic going in parallel with the pedestrians.

The most "famous" example in Europe of all traffic being stopped at once, I suspect is Oxford Circus in London, where they changed to start doing this a few years ago.

The reason to do it there, though, was to allow pedestrians to walk in any direction (diagonally as well) across one of the busiest crossings in the country. This BBC article refers to it as a "Japanese-styled system":

http://news.bbc.co.uk/1/hi/england/london/7997569.stm

There are a few of those intersections in the US and Canada as well, normally called "scramble" intersections here I think.

Most sets of traffic lights in the UK allow diagonal crossing, as in all traffic stopped at once, it's just not that common to encourage pedestrians to cross diagonally. What you never get in the UK is the condition described above, where pedestrians and drivers are directed to use the same bit of road.

There are also plenty of junctions where some car drivers are allowed to proceed while on other bits of the road, pedestrians are allowed to cross. So (typically) each road into the junction has a central island and the pedestrian controls for each half of the road are separate. On those junctions, it's never safe to go across the middle as there will always be some traffic moving.

The problem with busy crossings is that if both cars and pedestrians have 'green' at the same time, and the traffic is busy (i.e., someone would be walking/driving for most part of the green light), then it's very inefficient for cars needing to make the right turn, that need to cross with the pedestrians. In some street plans (e.g., interleaving one-way streets w. no left crossings) the right-turn traffic is very heavy and has a separate lane; so delaying them is bad.

There are two okay solutions - either you desync the lights, so that there's some gap where the pedestrians have a red light but cars already/still have green, so that they can make that turn; or you make a 3-phase crossing; A-cars have green in one direction; B-cars have green in the other direction; C-all cars stop and pedestrians can cross across and diagonally. It works okay.

What's not a solution - 'right turn on red' doesn't solve it; this problem matters in heavy car/foot traffic, and in such traffic there aren't any safe opportunities to do so.

The difference between US and UK crossings is that in the US, pedestrians and vehicles are directed to use the same bit of road at the same time. Cars turning right or left on a green light have to look to see if there are any pedestrians crossing, and give priority to them. Then the US also has that weird rule that allows you to drive straight through a red light, as long as you are turning right, which has visitors staring in disbelief.

In the UK/Europe, green means go and red means stop, without the above exceptions. In order to make this work, pedestrian crossings are often segmented, with individual signals for each section. There are a few junctions where all traffic is stopped for pedestrians, but that is pretty rare. Most junctions just allow pedestrians to cross on sections where traffic is not travelling.

UK/Europe also has a lot fewer crossroads than US. Since the cities are older, and do not as often have a grid structure, there are a lot more three-way junctions than crossroads, which actually makes crossing the road easier.

To be clear, right-turn-on-red requires that you stop first, at least in any jurisdiction I'm aware of. That being said, it still increases car/pedestrian and car/bicycle collisions significantly, on the order of 100% [0].

[0]: http://ntl.bts.gov/lib/25000/25600/25603/DOT-HS-806-182.pdf

> Then the US also has that weird rule that allows you to drive straight through a red light, as long as you are turning right, which has visitors staring in disbelief.

This varies by location. For example: In NYS it's allowed unless banned by a sign, but in NYC it's banned unless allowed by a sign.

Normally after the pedestrian countdown is finished the light turns yellow, then red for traffic moving in the same direction. Traffic in the perpendicular direction then gets a green light making it unsafe for pedestrians to cross.

The issue is that vehicles moving in the same direction as the pedestrians can also see the pedestrian countdown and can use that information to determine approximately how much longer their own vehicle light will remain green.

The article suggests that that different drivers interpret the countdown information differently than the green/yellow/red lights and more specifically, and unlike the colored lights, different drivers interpret the countdown timer differently (some see 3 seconds and speed up, others see 3 seconds and slow down).

The article is correct, and it is a real phenomenon in LA where I live.

To address your question, which I (humorously) don't really get -- the pedestrians who have the countdown and the cars are moving parallel to each other. The drivers and the peds are both looking in the same direction at the countdown timer.

Pedestrian crossings in the UK are rather unusual compared to most other countries in the world, in my experience.

In most places, crossings work on a parallel/perpendicular system: parallel roads and pedestrian crossings are red or green[1] at the same time. This means that cars turning across a pedestrian crossing must give way (yield) to pedestrians.

The UK system, by contrast, isolates the pedestrian phase from traffic phases: when the green man (the WALK indicator) is displayed, no vehicles will approach the pedestrian crossing from any direction. The time between pedestrian crossing opportunities is longer, but there is no contention for the crossing from cars turning into the road.

The article describes the parallel/perpendicular system. In this scenario, a driver will see a parallel WALK light and a (vehicular) green light at the same time. As the pedestrian crossing typically goes red earlier (because people take longer to cross the road than cars take to cross the intersection), a car driver who watches the pedestrian crossing light or countdown timer gains advanced knowledge of the parallel traffic signal.

1. Or white in some places in the US!

New Zealand has a mix. All stop, all direction crossings are usually reserved for downtown high pedestrian flow intersections.

There is also a distinction between green and green arrow turns. Green arrow indicates safe turns and green means yield to traffic/pedestrians.

I like how traffic is kind of organized in Paris: Pedestrians will cross the street whenever they feel like and don't care much about the signals. Because of that car drivers will constantly watch out for jaywalking people, drive with responsible speed and rather stop too often than being cited for reckless driving. All in all this works out extremely well and I always feel like this the safest city for a pedestrian.

It's possible that the lowered rate of accidents involving pedestrians can at least partially be attributed to the fact that drivers can see the timers.

Good grief.. the article ends with "Install them so that the pedestrians are aware of the timers but the drivers are not. And one way to do that would be to broadcast the timers via audio so that the pedestrians can hear the countdown clock go down, but drivers cannot."

The defacto standard in the Netherlands is that a pedestrian stop makes a loud ticking sound to aid blind people.

When its about to jump to red (lets call this orange) the pace increases, before going calm (not loud, and low pace) when the light is red. The orange period is -say- the time it takes an elderly lady to cross the street.

Here, we dont need countdown displays. People should be able look at the oncoming traffic instead.

quite a lot of lights in London (uk) have a count down for the pedestrian side - its just the nutters on fixed wheel bikes who blast through junctions at 25-30mph you have to watch for.

If you think I am kidding about the fix wheeled bikers visit the junction next to Holborn tube.

I'd like to see a study of red light countdown timers. I have only seen them in China, but I think they are awesome. The timer tells you how long until the light turns green. If it is 30 seconds, you can check your text messages, or adjust the radio, but when it hits 3...2...1... everyone goes at the same time. I have never seen so many cars make it through an intersection in a single light cycle.

I have a feeling it is good for safety as well because drivers get some downtime, and a timer that lets them know when they need to be back at full attention.

And then you have the dicks who will move at -1 second and jump the lights without checking that it is clear.

Well, this can be solved by well-known practices of red light cameras and revoking licences for repeated violations.

I mean, what you describe isn't a problem with timers, it's a problem with some dicks that are dangerous to others (not only in this situation but others) and should be prevented from driving at all.

Even when the intersection doesn't have the countdown timer, I memorize the number of "hand flashes" before the light changes and use that to figure out if I need to speed up to get through. This is on a bike, though, so hardly life threatening. The timers are actually very convenient, especially in New York with long yellows and long 4-way reds. 1 second? More than long enough.

In this context, it's a "cheat" for drivers with greater awareness, and one can't assume the driver in front knows to accelerate. Perhaps it would be safer if the timers were installed on the drivers' traffic lights as well. I've seen them in China and I liked the idea. What's stopping automobile traffic timers from being installed in the U.S.?

We have pedestrian walk timers here in Phoenix and they are very easy for drivers to see.

The situation described in the article happens when a driver is approaching a traffic light which is green but notices that there is only 1 or 2 seconds left on the walk count down and decides to stop. A driver behind, who may or may not have seen the count down isn't ready for a car to begin stopping as it approaches a light which is still green. Bang.

So the problem is not aggressive driving, but tentative driving? Wow.

Actually drivers have a duty to stop for vehicles ahead of them at any time. So the rear-ender, not the rear-ended, is at fault, even if the rear-ended was doing something dumb like looking at pedestrian signals.

I think you've slightly misrepresented the second driver's intentions. The article says:

"...the guy behind, he sees the two or three seconds and thinks, oh, the guy in front of me is going to floor it too, I'll floor it and we'll both get through the intersection. Whereas the guy in front thinks, OK, I only have two or three seconds left, I'm going to slowdown."

So it's not that the driver in front sees the timer and stops during a green light, whilst the driver behind doesn't see the timer and isn't expecting to stop during a green.

More likely that both drivers see the timer and make conflicting decisions: the driver in front decides there isn't enough time and slows down; the driver behind decides there is enough time and speeds up, having assumed the driver in front would be doing the same.

However, your scenario is plausible too and just as problematic.

Can't wait till we get self-driving cars. Next generation will find it completely reckless that we put people in charge of driving cars

Weird. I wonder if this is primarily a problem in larger, more congested cities where people tend to drive more aggressively. I live in a smaller city where we've had these a very long time, and they don't seem to inspire the kind of behavior they're talking about here. But driving here is also significantly less aggressive than somewhere like, say, Chicago.

I'm sure culture matters a lot - here in DC, there's no stigma or enforcement against running a red light or blocking the box so people do it all the time. This kind of behaviour is completely unsurprising but will probably reverse as the number of red light cameras goes up significantly.

I wonder if there's any weight to that assertion of a correlation between city size and aggression.

I live in London and I generally find that the behaviour is surprisingly courteous. My suspicion is that it's because many (most?) roads are actually too narrow to have two cars pass at the same time so people are very used to having to pull over to get out of each other's way.

Obviously, all totally anecdotal, but there must be some research on it.

With all this focus on self-driving cars, nobody is looking at the low-hanging fruit - cameras on the traffic lights. No, not for ticketing people, but for changing the signals in a way that maximizes flow. This will save time and an awful lot of gas. With all the sophisticated camera algorithms these days, this should be a relatively simpler problem to detect the speed, number, and distance of cars coming from each direction.

It can also be used to save lives - the light for the cross street need not turn green when the other turns red if there looks like a car is going to run the red. If there are pedestrians in the intersection, the lights can also remain red.

You can detect speed,ount and types ofcas with a pair of inductive loops (car length determines the type pretty well). I'd guess that putting such a pair some distance before the intersection would be a lot simpler (cars would obscure each other in the camera's view). That said, this would give you information about cars passing a single point on the road and would give you no information about pedestrians.

This has been implemented for some traffic lights in Warsaw, and has one more bad side effect (possibly because of bad implementation): if you a bike in the late evening on the smaller street, that's configured "red unless there's a car that will be crossing" to maximize throughput of the bigger street, you have to wait for a car or use a pedestrian crossing, because the loops won't detect a bike.

Lots (most?) of the traffic light controlled junctions in the UK have induction loops to detect cars. I have personally complained to the authorities about their lack of ability to detect bicycles.

Inductive loops, wires, maintenance, etc., are far more expensive than a $10 camera, once the software is developed.

There are/were a couple of junctions in Phnom Penh where the traffic lights for the roads have count down timers on both the green and the red. All the motorbikes started going around the 5 second mark meaning there was a good few seconds of everyone going from both directions. I'm sure it's pretty dangerous, but it was fun to navigate

Seems to me they could put blinders on the crosswalk timers so they are only visible from the corner and not from the middle of the street. They already often do similar things to left turn lane arrows (so that when you aren't turning left you don't see green out of the corner of your eye and jump the gun).

As a driver, I really like these timers. I can see from a block away that I've got 15 seconds (and will make it comfortably) or 2 seconds (and may as well slow down now since I won't be anywhere close).

As long as the blinders weren't too restrictive, my use case would still be viable.

That's exactly the use case that they caution about--drivers at different distances interpreting the signals differently, causing accidents.

The use case they caution about is drivers reacting suddenly to short clocks -- flooring it or slamming on the brakes -- when they're very close to each other. They're talking about how people react to a "2" when they're 2.1 seconds away from the intersection and right on somebody else's tail.

I'm talking about reacting from a long distance out by subtly adjusting speed (obviously in conjunction with reading traffic -- you don't accelerate if there's a vehicle right in front of you.) If you're 10 seconds out and see a 2, there's no differential reaction, likewise if you're 10 seconds out and see a 20. Even if you're 10 seconds out and see a 9, the difference between "slight acceleration" and "slight touch on the brakes" isn't significant unless you're already driving too close for the circumstances I drive under.

I've never seen a normal intersection where the pedestrian timers are visible to the drivers that are driving on the same road the pedestrians are crossing. The pedestrian timers are always lights behind a direction grill. I suppose the problem could manifest for drivers wanting to turn onto the road the pedestrians are crossing, or strange intersections where the angle of intersection is far from 90 degrees.

Here in Auckland, I think we only have those countdown timers at intersections where pedestrians can cross in all directions at the same time, so there are no cars speeding up to make the light, all of the cars are stopped.

Seems like they could easily fix this by installing some kind of small plastic guard to keep most cars from seeing the countdown.

In London we have the opposite, timers for how long you are allowed to cross, this probably makes more sense.

Why can't they just install more speed-bumps? Scientifically calibrated so that they only cause damage to cars going beyond an acceptable speed for the particular intersection in question. I used to live somewhere hoons would regularly speed by; a speed-bump was built, and it put an end to such speeding almost instantaneously as all the hoons had their vehicles' suspension destroyed.

Why can't they just install more speed-bumps?

Off the top of my head:

- Given the variety of suspension systems in cars (and available aftermarket options), trying to make a speed bump targeting one speed (or even a relatively narrow range of speeds) would be pretty difficult unless you want to limit all traffic to 10-15 mph

- Speedbumps on major thoroughfares can cause problems for emergency vehicles

- (from personal experience) riding over a speed bump (certainly ones that haven't been well-maintained) on a bicycle is not fun

- they make snowplowing more difficult (but not impossible)

Why don't they just retrofit these signals so that pedestrians can see but drivers can't?

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