Ask HN: What are you working on? (February 2025)

I live next to a school, so there's a low speed limit (30 km/h). Still, people drive like race drivers and the city hasn't ever responded to the residents' hopes of introducing a speed camera.

I wanted to have some data on how many people speed, the max speed recorded, that sort of thing. Things the city should be doing after many complaints of dangerous driving and people being almost killed on zebra crossings.

I have a doorbell camera, and by analysing the footage using OpenCV and some code, I can track how fast people drive if you see how fast they move between two known points.

Average speed: 46 km/h :(

I'm interested in this. A modern version of community watch.

Man, please share a tutorial

What about placing a fake speed camera? It might just get the job done

Is that legal in your country? In mine (Netherlands) there are way too many people with doorbell camera aimed right at the street even though it's illegal to record a public space like that. Most folks are ignorant about it though, or think that surely the internet-connected gadget sold by some anonymous corporation won't be abused....

Not sure where you are, but 30kmh sounds Dutch. Filming the public road from your private residence is illegal.

In practice, no one cares. Cops will even ask you nicely for footage if something went down in your street.

Anyway, best of luck with your project.

It's a complex discussion in the Netherlands in which the data protection agency (AP) has a very strict view (they claim it's not allowed) while for example the associated press sees it very different.

There is a key difference between recording vs publishing. There are more restrictions on publishing and an objective assessment needs to be made between the interests of the person in the footage and the general public or publisher.

I would argue that recording the road to collect speed data, not keeping the recording longer than needed and not for example recording license plates, would pass in the Netherlands. Since you're making an assessment between different interests and the is limited privacy impact. Of course assuming this is happening on a public road and not someone's property.

Publishing the recordings instead of just the average speed data would be a very different story, especially if the cars or drivers can be identified.

I'd rather put up with the speeding than aasking for the government to intervene.

Government is already intervening, you think people are going at only 46 kmh because of goodwill?

Ooh how edgy.

For private use you can film in public places in the Netherlands no?

Said someone living in a comfortable country with a stable government.

You can’t seriously believe this right?

i think part of the problem is 30mph/48kmph doesnt feel fast - and to get people to drive slower manufacturers need to design cars so 20mph/32kmph feels faster

It is the "systemic/constant/permanent" recording, record-keeping. etc. a.k.a. "processing" (GDPR "processing" means "if it exists and you touch it, your are processing it").

Back in 2005 I remember working with some physical sec company that were setting up cameras in a factory, and they wanted the cameras to 'not record traffic, be activated on if THIS part of the screen has motion')(sidewalk vs sidewalk-right-on-our-doorbell vs road). Also, sudden changes in lighting would trigger it :)

Then you need to have retention period (good luck). Most people use those door-cams are violating GDPR. UNLESS when people complain and take you to court (very very very rare), you can prove that "I auto-delete records after 24h when there is no incident", "I have proximity scanner so it is only 0m-2m from my front door", etc.) (violating GDPR because "hey you pervert why do you record my kids EVERY DAY going in and out")

Privacy and Data protection is very very very difficult with GDPR (and thank you Facebook for messing up back in 2015ish!!!)

You can set up your cam but have the "AI" automatically pixelating all license-plates, and the video recording (if any) should be post-pixelating, and not the original feed. How about you put something with a speed-measuring-sensor (that is NOT a camera), so you only get 'anonymised' data, i.e. "20 moving items", and their speeds. But you will not be able to tell if the 300km/h was done by a bicycle or a Hayabusa ;)

Can you post this code if possible please?

The guy at Not Just Bikes will tell you that enforcement will never work nor happen and that the only way to get people to slow down is to design the road so it doesn't feel safe to drive fast.

The road next to my house has a speed limit of 20mph but most cars go 45mph because it's a straight road 4 lanes but space for 6. No bumps, no curves, wide. Effectively it feels like you should be driving fast. If I go the speed limit in the center lane because I'm going to turn left people will get angry and speed around at 60mph pissed off

Or consider the width of the road...

Has anyone been hit by a car there ever?

I think people used to use science to set speed limits.

There are plenty of tutorials on how to derive speed of an object using opencv. You could ask an LLM to write it for you.

There is optimum level of state intervention. IMO monitoring people with cameras for speeding is a step too far.

I bet you are the same type of person who values software privacy haha

You are not allowed to put up unlicensed surveillance cameras in public places, no.

Publish to Twitter along with number plates and tag the local council.

What about just faking speed limit signs? If it's in The Netherlands, everybody should respect traffic signs, whether they are fake or not.

There is another way: make the road feel fast. Thankfully it doesn't need to be via bad road surfaces or horrible things like speed bumps that only encourage boy racers and reward large vehicles, making the road narrower with high kerbs or other physical obstacles force drivers to drive slowly and pay attention, otherwise they'll physically damage their vehicle. In a way it evens the playing field, currently cars can kill you, but they are untouchable, there are no consequences for speeding or being distracted. The main downside I can think of is the route becomes difficult for emergency vehicles to use, but with the saved space there could be a dedicated lane for public vehicles.

Just out of curiousity, do you signal that you are going to turn left when you slow down compared to the average of the other drivers?

Possibly illegal, depending on where you live.

I'd think that as long as you blur faces and license tags, would be there anything for someone to complain?

I'm starting to think about a similar thing for noise. The noise of motor vehicles seems to be out of control and I am sure it is causing misery for the majority of the population who have to live near roads. I reckon a single loud motorcycle could disturb tens of thousands of people, potentially waking or startling them, raising blood pressure etc. in a single 10 minute trip. Unfortunately I think awareness of this problem is even worse than speed.

Then why even have speed limits if you don't want to enforce them?

You sound like someone who doesn't have young children who cross a road where the road users should be respecting the speed limit set deliberately low because it's right in front of an elementary school, but instead a significant proportion of them are Michael Schumacher wannabes who need to drive everywhere at 60km/h.

I don’t know about this person’s experience, but there are an overwhelming number of drivers here that don’t notice signals. I can be in the right lane (two lanes in both directions), signal a right turn, slow to turn and they’ll still ride right up on me and look pissed rather than go around.

No need to have children. It’s the same crap in France and I have to be very careful not to get killed when I’m driving myself. These morons don’t care about kids but they don’t care about other drivers either.

I’m a big privacy advocate but when you are handling a killing machine on a public road, there is no privacy IMHO.

GDPR says no. Also, when you are using a cloud service it is no longer private use, you are sharing the surveillance video with Amazon (and almost certainly with the USA three-letter agencies) too.

I think that's simplifying things too much: as a driver, there are also pedestrians who will jump out into a street without so much as looking where there is no crosswalk; there are also drivers who will drive 20km/h in a 50km/h zone, and you have no idea what's going on except that you are likely to hit 5 red traffic lights which are designed to be a "green wave" and make a 30 second drive through one street into a 5 minute one, and resulting in more gas usage and more pollution.

And yes, this type of driving will produce annoyed drivers that "drive crazy", and I don't accept that this is just their fault.

Mostly, these same drivers doing 20km/h will not even stop for pedestrians on a crosswalk — slowness does not equal attention and safe driving!

Traffic, in essence, is a collaborative effort that requires all participants to be empathetical to other participants — as such, we need to be most mindful of the "weakest" participants like pedestrians (especially kids, who can also be very inattentive), cyclists, motorcycles but also of other car drivers — if we care about each others' experience, we'll reduce the risk for everyone involved, while getting everyone where they want to go in a timely and efficient manner — and that is the goal!

This is very interesting. I had the same need a few weeks ago, which resulted in a tiny Golang/OpenCV project (https://github.com/kmmndr/motion-speed). In my use case, we even had champions beating 60 km/h, three times allowed speed

On paper it's illegal to record the public street, but it seems to be given a pass for doorbell cameras, even going as far as the police asking people to sign up theirs into a database so they can request footage if needs be [0].

[0] https://www.politie.nl/onderwerpen/camera-in-beeld.html

There will be speed limit signs, but they're easily ignored. Maybe one of these plastic "watch out for our kids" things that people place on the street themselves? https://verkeersmaatje.nl/

They did, 30 km/h is a lot safer than higher speeds. You seem to imply someone has to be hit by a car before enforcing the speed limit, am I correct?

Ironically, the lower you are to the ground, the faster it feels - everyone should drive a sports car!

(conversely, I drive a motorcycle sometimes which puts my head at or just over roof height of most cars, it makes 80 km/h not feel as fast. Mind you, the added road overview also helps)

Anyway. Narrow / winding roads and speed bumps will definitely make you want to drive slower. We have 'cars are guests' roads inside cities too, which are roads designed and coloured like bike paths (= red asphalt).

But the opposite is also true; I got a speeding ticket once, the road was a 4 lane, separated directions asphalt ring road... but the speed limit was 50 km/h.

The speeding itself isn't the problem. The increased risk of accidents is - and since this is around a school, it involves young children.

"I'd rather put up with the speeding" implies you don't have kids and you only consider the noise nuisance, not the safety risk. Very self-centered.

Also a sure-fire way to get some irate drivers banging on your front door, given that it would be easy to work out which house the photo was taken from.

> I reckon a single loud motorcycle could disturb tens of thousands of people, potentially waking or startling them, raising blood pressure etc. in a single 10 minute trip.

What absolutely grinds my gears is when a loud motorcycle or sports car drives through my residential neighborhood right after patiently rocking my baby to sleep.

Interestingly, as a motorcycle and sports car owner myself, I never thought about that aspect for even a second until I became a dad—I drive much more gently nowadays (especially in residential neighborhoods)!

On my street they installed one of those 'current speed' radar displays to let people know they are speeding.

I've never thought they worked really, but this is a new one. It has very prominent red and blue flashing lights that trigger if you are 5+ over. I've seen countless people slow down immediately, it's that jarring/terrifying

> Interestingly, as a motorcycle and sports car owner myself, I never thought about that aspect for even a second

Right, because the car's cabin and motorcycle helmet protect the driver/rider from it. The noise they create are specifically designed to be heard by everyone but the operator. It's like me sitting in my back garden wearing earplugs, while blasting music out the front into the street.

It's always interesting when you find out others are doing some obscure idea. Last year I was scraping supermarket data from a small country and I ended up setting up a discord with a half dozen of us sharing tips.

the side effect is bikers like me will pedal as hard as possible in hopes we can get that light to flash

It gets worse, some drivers seem to adopt an adversarial attitude towards the usage of turn signals and will deliberately accelerate or do something else to make things more difficult to you.

That's because a lot of those people think it's a "speeding ticket" camera flashing at them.

Yeah, unfortunately this is true. A street near my house has a limit of 40mph and people would regularly drive 60 mph+, sometimes someone would pass me doing 65+mph (it's a no-passing residential road).

Eventually someone died, and they added a lot of traffic-calming changes to the road. It's much nicer now, but a shame that someone had to die to change it.

>The guy at Not Just Bikes will tell you that enforcement will never work nor happen and that the only way to get people to slow down is to design the road so it doesn't feel safe to drive fast.

This makes sense. Though annoying to drive over, speed bumps work. Also, my parents small town converted their main street from a four lane to a slalom-style two-lane and it so much nicer to walk around because people have to drive slowly. Not quite car-free, which I'd prefer, but it's a decent compromise.

It's not legal where I live (Belgium), it can be legal if you have a driveway and only film your driveway, and if you declare that camera in some database. But since I don't have a driveway, it films the street, I am aware that this is not legal.

It's my personal decision and if I ever get fined for it, I will gladly pay the fine... with the money that my doorbell camera has already saved me. It helped me catch hit&runners that bumped into my parked car twice already, and the camera is now almost two years old.

It's not connected to the cloud, saves data locally, and only stores a couple of days of video. It's not very ethical to unknowingly film public spaces, I know. My lame excuse is that I personally think that catching people that damage my property with a camera is a lesser crime than damaging someone's property and running away. The sad truth is that living in a place where parents drop off and pick up their kids twice a day do not give two shits about others. Hit and runs happen every day here.

Agree, but also disagree.

Our neighboring town has a beautiful system in place. It tracks your average speed over +- 100m. If you speeded, you get a fine and even better: the light always turns red and you have to wait for a minute. If you run that red light, you get another (heftier) fine. If you drive normally, the light is always green.

It's beautiful. People actually drive slowly and safely there. And good, because that system is installed perfectly around the school and doesn't hinder anyone else. If they did this anywhere else you'd argue it's a moneygrab, but this is imo a great way to actually get people to drive slow in a school zone.

In contrast the only thing our town has done is install a bunch of big concrete flower boxes (?) that hinder your vision and causes conflicts on the road. The idea being that you'd have to slow down and that you're no longer on a straight wide road. It's absolutely only made things worse. You need to give way to others but you literally can't see them, or you need to pull weird manoeuvers to let them pass. And in the meantime cyclists need to swerve around them or are hidden behind those boxes. It's terrible.

They did try this approach. There's big concrete flower boxes in many places to create some artificial hindrances. It hinders your vision, causes people to swerve, it's annoying to give way. And worst of all: it slows people down for 2 seconds after which they just floor it.

Honestly it's already pretty narrow and crowded here. I'm a regular driver here (duh) and it honestly feels dumb to drive faster than 30 because a cyclist can pop out of every corner. It's crazy to me that people want to, and do drive faster than that. But here we are. People suck.

If they’re behind me, they’re risking their own liability.

Otherwise (changing lanes, left turn across traffic), I think it’s more “not ahead of ME!” than about the signal itself.

you could install some vigilante speed bumps maybe

What is a licensed security camera?

By this logic, are you saying cameras on private property, that happen to capture public space in their frame are also illegal?

GDPR just gives you the right to have it removed right? Curious to try that out, and request Amazon remove you from every ring recording .

Then can make a video beating them up and post it on twitter.

As others have pointed out, you are essentially advocating for non-enforcement of speed limits.

Which feels an arbitrary line to draw. What about other road rules? Driving on the right side? Using unregistered vehicles?

Countries like India, China and South East Asia, have much less enforcement of these rules… Would you call their driving experience optimal?

Not sure what you mean by values software privacy. I don’t really have a view on it? So no, I don’t think I am.

If two cars travelling the same direction contact each other such that the front axle of one car bumps the rear axle of the other (the car in front), it's usually the car in front that has the safety problem. This is the same principle behind the PIT maneuver.

No, just implying that when someone is hit that the posted limit has more scrutiny.

Speed bumps are a crazy invention because they tell you what humanity is like. Let's make this road worse for driving because many drivers don't care about safety but do care about damaging their cars. I am reminded of this every time I see a speed bump.

I used to live in a neighborhood about a quarter mile from a highway, nearly perfectly flat land, speed limit I believe was 45 or 55.

Most days the road noise itself was no big deal, if the wind blew it was gone, if you listened for it you could hear a whooshing/droning in the distance.

But all it took was one loud motorcycle or old car/truck to really ruin your peace for a solid 3 to 5 minutes, being able to hear it on approach, and it went by, and exit. And it wasn't that rare to get them back to back, seeing as it's a 4 lane highway with a decent flow of traffic.

It wasn't really until then I realized how a single vehicle could cause so much annoyance for so many people.

>Our neighboring town has a beautiful system in place. It tracks your average speed over +- 100m. If you speeded, you get a fine and even better: the light always turns red and you have to wait for a minute. If you run that red light, you get another (heftier) fine. If you drive normally, the light is always green.

I have never seen a system like that. What town? Or what system?

Of course it is. Is this controversial anywhere? I would expect surveillance cameras to be regulated in most parts of the world, certainly around Europe. In the Netherlands I believe you need to register such cameras with the local police and you are responsible for following the relevant regulations and data protection laws.

Irrelevant. They're going 45+ in a 20mph zone.

Sounds great! Now if I could just get that installed in 100% of California

ATM we basically have lawless highways in California. Every time I go out I see outrageous traffic violations. People driving 15-20 mph over the speed limit on the freeway, weaving in and out of the carpool lane. People pulling into the left turn lane at a signal, then just crossing on a red light as soon as they think it's safe. People passing in the gutter (no lane). People cutting across 3-4 lanes of the freeway at ~70mph, across the painted barrier to exit a freeway.

I'd say the average of these incidences I see is 3 per drive and that doesn't include just you average weaver or tailgater. In other words, I take my car out for a 10-15 minute drive, (so 20-30 mins round trip) and see someone do something outrageous endangering other people's lives 3 times per drive on average.

Many places on California are more or less lawless, not just the freeways...

This reminds me of the civic minded heroes from Oakland, the Pothole Vigilantes:

https://www.youtube.com/watch?v=ZmCNMQ7TOgY&t=9s&ab_channel=...

Our street is fairly bad, and I've brought it up to the city several times, so one of our neighbors went to the city and managed to get a vote for some speed "calmers" put in. It passed! A small example of government working for the people.

It's a basic trajectory control system (using ANPR cameras), combined with a red light camera. They read your license plate twice in different locations to determine how long you took to drive a section of road. They're very common here in Belgium, but it being coupled to a red light is not that common. They even have a sign that says "too fast = red light + fine".

I think main problem is that half of adult men population is actually into those noisy/auto-moto sports. Even if they don't own one, they like and admire this silently and believe it's harmless nuisance. Add to it few friends that already do it ... and they're cool...

I live in EU city center. Stupid noisy speeders are bane of my existence. Both noise and safety (for biker and pedestrian) ... In some circles even raising this topic makes you whining leftist crybaby.

Do you think the government does not track your car already?

Much easier to lecture private citizens about privacy than the government ha.

Sounds like it's an issue with the speed limit.

Video surveillance limited to your own private property is not actually subject to GDPR. See GDPR article 2 para 2 lit c. It's not my asswipe opinion, either, see this whitepaper from a state privacy commissioner: https://www.datenschutz.sachsen.de/download/Hinweisblatt_Vid...

I assume you are talking about cyclists. So in this case i guess it's not a biggie as they are moving the mass of no more than 20kg compared to 2000kg when driving a car. (from safety perspective)

Reminded me of this: https://www.youtube.com/watch?v=rReyh1wnl8I for the Malcolm in the middle fans!

I am not from the US but have driven a lot more in the US than the average tourist (maybe x0,000 miles). What amazes me is not only those traffic violations but how often they're justified on forums (including HN) because of things like 'it's unsafe to drive the limit when everyone's going faster'. Over there, people seem to drive with a deathwish.

It's quite jarring to come home and drive an expressway in South Australia where the "speeders" are doing 105 km/h on a 100 km/h route. Someone doing significantly more is a rarity where I live.

I don't think that's necessarily true if it's a street also being used by cyclists, crossed by pedestrians, etc.

If there's a rear end collision severe enough that the axles are contacting each other, both parties have a safety problem.

I wasn't talking about that. I meant lateral motion

Yes it requires collective empathy. There was a time when we never required the nanny state to constantly watch over us. A sign of a high functioning, free and unified society is that you shouldn't need be forced by the hand of the law to conform to the lowest common denominator.

Is it really a beautiful system if it involves adding and maintaining a completely unnecessary traffic light? That isn’t free and costs tens or hundreds of thousands of dollars over its lifetime.

I’m not saying it’s not worth it, even 1 life saved would make it worth it, but it’s not beautiful.

No, they're going 20-something mph in perhaps a 20mph zone: the author stated kilometers per hour.

I didn’t mention safety issues

What you are suggesting is basically unenforceable. How would you know what’s in a cameras frame?

What do the police do with that register? That sounds like it’s just helpful for them. If it’s only a registration and not an approval process?

I don’t think you are responsible for data protection laws… like if it’s a ring, that’s amazons problem.

I think this is controversial, because how’s it different from me taking a happy snap on my phone and accidently capturing you in the background.

I remember in Europe saw a lot of roads constructed that way to prevent fast driving, e.g. lots of small roundabouts. It works pretty well.

How are they similar? One is taking a picture, one is a permanent installation recording every movement in a public area.

What country allows citizens to mount private surveillance cameras in public places without a license?