85th Percentile Rule (where applicable): In many states, a common engineering principle is to set the speed limit near the speed at which the majority of drivers travel under free-flow conditions. Some states adapt or supplement this approach with safety-oriented judgments.

https://thelegalguide.org/who-decides-speed-limits-federal-state-local-roads/

Cops aren't people though

It’s one of those areas where we want to regulate something we don’t really want to, so we’re stuck at a compromise that nobody says they are happy with but also nobody wants to change.

We set speed limits (so we did something about traffic deaths), but we don’t enforce them, because drivers would hate that. The upside of the existence of speed limits is that reckless drivers can be charged with speeding if they cause an accident. The downside is that police departments make a revenue stream of ticketing citizens driving at completely safe and reasonable speeds.

Some parts of Europe have automated average speed cameras. That’s way more draconian than a speed camera: they take a pic at each checkpoint, they know the distances between them, if your time is better than what you could do by driving at speed limit, you get a ticket. I would go nuts if I had to drive like that. It would work for autonomous vehicles, so I expect that systematic speed limit enforcement will coincide with the rollout of autonomous cars, which will be the time to stop driving on public roads anyway.

Another similar area is immigration, sorry for the off topic tangent, but I think it’s a similar dynamic. Anti immigration politicians say they want to make tough laws that keep immigrants out, but the laws are not enforced, because without immigrants entire sectors of the economy would stop working. Progressive politicians say they want lax laws so everyone is welcome to enter, but that would be a shitty law because you can’t run a country without borders. So the likelihood that we end up with regulations that allow the right amount of migrant workers and respect refugee rights, and then are actually enforced, is about zero.

Speed limits are designed for suboptimal road conditions. Since dynamic speed limits weren't even possible until relatively recently, they figured out how quick you could safely travel on a road when it is nice, and again when it's crappy, and set it somewhere between those values.

1. Because the average American believes speed limits aren't meant for the especially skilled drivers like themselves.

2. If the speed limit is raised, then people will drive 10-15 MPH over the new limit. Natch.

3. Traffic enforcement cameras have been routinely abused by the government and so have to be regularly taken away from them like the naughty children they are.

4. People will assure you that civil planning has done their job and everything is already working like a well-oiled machine. I don't know why people keep saying this when it's obviously not true. It's astounding.

👆

...as a licensed US driver who finds public transit much less stressful.

Uh yes, traffic calming.

Wait, they are like that in the US? In many European countries (I know it's the case in France), the speed limit is explicitly for good weather, and there's a lower limit when it's raining for example (highway is 130/110 km/h, but in rain conditions the limits are 110/100 km/h)

No they’re not designed for some average they are for “good conditions”. I live in the US in the Pacific Northwest where it rains a lot and a big part of learning to drive here is that yes, you do need to slow down when it rains the speed limit is often not safe when your stopping distance gets extended by wet roads.

That sounds like something drivers tell themselves to justify speeding. Any source on that?

Mostly politics and grafting. There is a piece of highway in Florida where there is a nonsensical low speed limit. The stretch is "owned" by a little village with a police force nearly as big as the population in total, and the police is basically generating a good income by speed trapping on the highway 24/7.

Yeah so true, ultimately we don't have much control over our interactions with police, ugh

And the reason most places in the US don't standardize is because we have too much traffic in populated areas. Despite forcing semi trucks to stick to the slower lanes, some will move to the fast lanes either to pass other slow trucks, or just to make up some lost time on their route. Which keeps all traffic at safe truck-driving speeds anyway.

Also an issue in Germany. We call that practice "Elephant race" because those massive semi trucks will hinder any other traffic at passing each other until the 5 km/h faster truck passed the other.
And that does take a while.

1. where I grew up, we didn't. I also grew up in a state that was always in the top 3 for speeding fines given.

2. Because, at least in theory, speed limits in the area should be set for safety, not desires. The US is generally really bad at safe road design (e.g. less wide and straight in residential and similar areas) which enables those speeding

3. fees based on things like net worth and/or salary would theoretically help. That will never happen though. Some places use cameras to offer civil penalties, but I'm not sure where camera enforcement is otherwise legal. I haven't lived in the US in over a decade, though.

4. ah, yeah, I wrote my point 2 before this. The US is way too car-brained and me-centric for that in many areas.

That said, where I live in rural Japan, people customarily go 10-15 kph over the limit and pass like idiots even in 30kph residential areas. The police seem to mostly only give a shit during specific enforcement campaigns that happen a couple of times a year. I try to walk, cycle, motorbike, and drive in that order depending upon what I need to do and where. Even on my motorbike, it can be scary on our roads.

1. Idk human nature or some such
2. Because then people will go 10-15 mph faster than that. Believe it or not, speed limits are actually chosen with the understanding that people will go 10-15 over. Thats why going 10-15 over is almost never enforced and driving the exact speed limit is seen as an act of aggression.

I'm going 10 miles above the limit on this incredibly wide and straight and flat road with high curbs and perfect visibility

This is the reason why people speed. If you want people to drive more slowly, you have to design the road/street in a way that discourages higher speeds. Do this, and you won’t need any invasive speed cameras or pay traffic cops to enforce.

On highways I suspect no one gives a shit. If it feels natural to drive 10 mph above the speed limit, it’s probably safe. But raising the speed limit would probably lead some people to speeding even more, with fewer options for punishing them (in my country at least, the fine is dependent on how much above the limit you were going).

There's a very short expiration date on intentions. After that, they're just PR for the system's true purpose.

All engineering is built around tolerances. You don't build something that just barely handles the expected use case, you as a significant buffer.

Bad conditions would still because allowing down from the average... That's how math works.

Traffic enforcement cameras have been routinely abused by the government…

People focus on the nasty abuse like stalking etc. but in my experience traffic cameras (specifically stop sign cameras) are abusive in another way: the fines are low, the crime is classed as civil, and no points are added to the drivers license. Which means if a citation is issued, people just pay it because contesting a false positive case is impossible because you have to schedule a court date, take a day off work to go to court, and pay the court fees even if the judgement is in your favor (which are higher than the actual fine). This only gets worse as more of these cameras switch to AI flagging with “human review,” which we know translates to “no one fucking watched the video, they just isssued the fine.”

Usually the people involved in the system continue to have intentions.

This whole thing is so idiotically, purposefully failing to understand real people. Like AS IF you have never supported anything imperfect and wanted it to work in a way different than how it actually works. Nobody applies this consistently.

I don't speed.

I mean I do, but only if I'm not paying attention. I naturally want to go fast. If there were no cars on the road, I'd be going as fast as I want. During the pandemic, when no one else was on the road and cops weren't pulling people over, I was getting to work in 30 minutes. Normally it takes no less than 45, and usually more like an hour and a half.

However, I don't speed because there are other cars on the road.

I'll drive at the speed limit if I can. I used to drive about 5 mph above the speed limit, but the last time I was doing that, I stopped for a school bus dropping off kids, and the guy behind me didn't even stop looking at his phone (I assume). And it occurred to me that he was going 5mph faster than he would have been because I let him.

So now I try (again, fighting my nature) to never go above the speed limit. I also never drive closer than 4 seconds to the car in front of me. I also very slowly decrease my speed down to 10 mph below the speed limit if someone is tailgating me.

Prior to the pandemic, people would be annoyed, and they'd aggressively pass me when it was safe to do so. Since the pandemic people just cross the double yellow line into oncoming traffic to pass.

They've made it much harder than it used to be to get your license in PA, but it's still too easy to get and keep your driver's license. Every driver should have to repeat a driving test every five years.

My wife has health problems, and voluntarily stopped driving about 15 years ago when she noticed she was developing muscle weakness. The only time she's driven a car since was an early Sunday morning when I took her to the empty high school parking lot and had her drive our civic around so she could just see what it felt like.

My dad drove him and my mom to church on the day he died. He had been having increasing number of car accidents, but no one could stop him from driving. My wife and I refused to ride in a car with him driving. I think the last accident he had was with a light pole in a parking lot because "the sun was in his eyes."

If his heart had given out on the highway on the way instead of in church, my siblings and I would have had to bury both parents.

Give most humans an inch and they'll take a mile.

Wow, such wrong info and opinon here. I swear, Lemmy might be worse than Facebook to find out real info.

1. Because most devices that measure the speed of cars on a road have an error rate. They need to be calibrated regularly or they might be off by a few miles an hour. Calibration takes time, which means it's expensive.

https://schwartzcohenlaw.com/how-often-do-radar-guns-need-to-be-calibrated/

Meaning that there's little assurance that your speedometer and a radar gun will agree exactly. They might be up to 5-7 mph off. So if someone is going up to 10mph above the limit, it's legally not guaranteed that a radar gun reading their speed accurately will result in a fine.

Also, 10-15 over is about how far you can go that if you see a cop far off, you can slow down in time.

https://fightyourspeedingticket.com/types-speed-measurement-devices/radar-and-laser-calibration-issues-in-the-state-of-florida/

On top of this, fines are usually proportional to speed above the limit. So the fine itself is usually not worth the time or hassle to a cop if it's just over the limit. They prefer easy, slam dunk cases, like someone doing 35 in a 15, or 65 in a 45.

1. In the US, speed limits are based on road engineering, sort of guessed tolerances for the shittiest cars on the road, and (way back when) fuel economy. So it's a patchwork of things unevenly applied over decades. Not all these standards change in every state regularly. Not every state is in a rush to check if 1970s standards for car tolerances for grade on a curve are still helpful. Often not until someone has a reason to lobby state government to change them.

2. Until only very recently, a human had to weild the radar gun. Physically and legally. Most States didn't allow automated tickets until they saw how easily fines could be collected with them. Those systems are expensive to buy and very unpopular, so not every local government wants to be the people that put up surveillance state infrastructure - and made taxpayers pay for the thing that now gives them tickets.

3. Those are both expensive as well, and the if you did that, people would get less tickets. Which means lower local government budgets.

You're really looking at this from a backwards perspective. People want to do whatever they want. Then one rule shows up. Then another. Then another. Each one is imperfect, and so each rule and method gets expensive to implement, but also makes people feel hemmed in a little more. And each rule pisses people off because they have habits that work into the gaps of the old system.

Do you have any insight on the monthly costs? I mean it's just unbelievable to me that a camera in 2026 would cost $5,000/mo to operate. That's an insane cost. I suspect some kind of legalized monopoly.

And you know, I've read breathalyzers also have to be calibrated, and that's terrifying to know, because they're probably not, and they generate more revenue when they're off.

Your explanation of why speed limits are there are is basically saying there's multiple overlapping systems, so everyone gets to be right, and everyone gets to be wrong.

I sort of understand the argument about cops needing to hold the radar gun, but I also don't really get what they're contributing to the legal validity of the case. The issue in question is whether you are speeding, and that is entirely dependent on the camera. If the cop is holding it or if the gun is on a pole is logically irrelevant.

One thing I don't think I've seen people say is: we don't control speeding because people want to speed. Case study: Toronto. Legendary asshat Doug Ford removed speed cameras because they were politically unpopular.

Why does everyone drive 10-15 miles above the speed limit?

This isn't really unique to the US. In my country people also consider it their right to drive above the speed limit and hate the police for telling them they can't do it...

Why don't we raise the speed limit if that's how fast everyone wants to go?

Because then everyone would drive above that new limit instead. It's a psychology thing. It's not that everyone would rather go speed y than speed x, being above the speed limit is the very point to it. Otherwise you'd see different behaviors with different speed limits, but at least here, every speed limit sees the same behavior of people not respecting it by the same amount.

Even before AI was in the mix, local governments were pulling crap like shortening yellow light timers to less than their own laws require for safety. And fine citizens (or habitual yellow-light runners) did the leg work to catch this crap. We've always had to be on our guard. That isn't a new phenomena.

Because people want to get places faster, and everyone knows law enforcement can't reliably say if you were going 30mph or 40mph without a radar. So everyone collectively agrees that up to 10mph over the limit is fine since you probably won't get pulled over unless you go more than that.

If you raise the limit from 30 to 40, people will just end up driving 50.

Why does this improve safety

I knew i wasn’t crazy when my friend who is a lawyer said he was starting to take the bus to work because driving cars opens one up to too much liability.

It's not about monthly costs. It's about up-front costs. These systems can be millions, maybe tens of millions to start, and are typically a huge, multi-year contract to a third party company that manages the system. Plus hiring human staff, maintenance and installation of a huge amout of it systems, training, tying in the car registration databases... On top of the fact that they're politically unpopular. Most people don't want to be tracked everywhere they go, even if the trade off is slower drivers on the road. There's a lot of headwinds before monthly costs are ever even a consideration.

Speed limits aren't an "everyone gets to be right/wrong" thing at all. It's numerous new things added as band-aid and one-item "fixes" to specific situations. It's also why the US tax code is such a mess. No one cares to overhaul it, and it's just a huge jumble of singular tweaks. It's like when you let a group of people take 10 years to write a story, and every week 5 people get to add or edit 1 sentence. Will you get a harmonized story with coherent plot? Likely not.

Radar guns don't report the speeding to anyone. A radar gun sitting on the side of a county road will write a ticket... how? Magic? It's a tool. A tape measure doesn't measure your height for you, you have to read the number and know the context. Before radar guns cops had to base speeding on a guess, or their own speedometer, and had to testify in court to a more subjective standard.

We don't control speeding because we mostly have passive systems that fine people for violations. And anyone determined enough will speed anyway, fines be damned. Many people speed as a flex and pay fines like a status symbol. You can't engineer 200km or 200 miles of highway to keep people at 65mph or below. Engineering solutions are limited to pedestrian areas or slow speed areas. The systems we use to fine people have the added societal costs in that they take taxes to set up, and are surveillance state tools.

It's the ongoing maintenance, just like how calibrating cars to exact speeds is expensive, so too are radar and laser guns. So the burden is on the radar/laser guns because there are fewer of them. And the calibration cannot be performed on site, as the unit your testing against also has to be calibrated to a much higher degree and you're not going to throw it in the back of a truck and drive it around risking damage. And in the event of someone disputing, it's up to the state to produce proof of calibration rather than the individual proving it was not. It's an expensive process, as anyone who uses specialized tools (not limited to law enforcement) would tell you.

Now, it's possible that the calibrations aren't done, and people don't question them and get tickets. But you want the ones that don't constantly make mistakes. 20ish years ago DC put up cameras and it was sending tickets across the entire US because it wasn't reading plates correctly. They had to hire more people to cross reference any matches with the make and model of the car just to double check, and that was a lot of eyes that needed paying. Even though a lot of it is automated today, you're still paying a premium over putting a camera on a stick.

Why don't we raise the speed limit if that's how fast everyone wants to go?

Because then everyone would drive above that new limit instead.

I'm not so sure about that. If the speed limit in my neighborhood was 80mph I don't think I'd be going that fast much less above it. If the nearby interstate reduced the speed limit to 25mph I don't think I'd naturally be driving it at 35-40mph as you state.

In my experience, it's more a thing that I think many people disregard the speed limit for the most part and have a certain speed they feel is natural and comfortable for them to drive on a given road in a given situation.

Going through the neighborhood? Some people think 15mph, some think 25mph, some think 30mph. See some kids playing on the side of the road? Most people generally would slow down a bit. Roads are tight and narrow? Well now I have to be a bit more careful in this area so I need to slow down even further.

In my experience the psychology trick has everything to do with the road, what's around it, the condition it's in, etc, and less to do with the sign itself.

Well, I think both of you have a point. The problem with "most people would slow down" is that this means dead children because of those who don't.

Speed limits to have a role to play, however much better than a sign is indeed to create roads that naturally make people drive slower. Countless streets in Europe have been redesigned according to that principle, the most systematically in the Netherlands. Why? Because it works and it saves lives.

The US requires roads to built in a way that the "natural speed" would be insanely high, even in purely residential areas.

Honestly, at this scale, a resounding yes to your first question.

Bro you sound like a bad driver.

It's not your place to police other drivers and their behavior. Nor is it mine. Slowing down if someone is tailgating pisses everyone off, and going under the speed limit can be just as dangerous as going over. It's a really easy way to cause a crash.

Drive predictably. If that means going the exact speed limit, fine. But far too often I am on the road with people who think going 25mph in a 45mph on a two lane road is safer.

Yeah, I'm a believer in this. Inversely, I call it the 20% rule: You can go 20% above the posted speed limit safely. It works pretty much anywhere, although I tend to stick to 25 or below in residential areas, mainly because I don't like people buzzing by me when I'm walking or running on the sidewalk, so I won't do it back to them. But in a 35, 42 is reasonable. 78 in a 65? Not a problem.

Yeah, you're wrong. If someone is tailgating me, I'm going to reduce my speed to minimize the impact.

I've been hit. I've been hit by people who were tailgating me. When that's happened it didn't matter what I did. If I speed up, they speed up. If I slow down, they stay right there. I've literally turned on my hazard lights and had people continue to tailgate.

It's not about policing other drivers. It's about minimizing the damage they will eventually cause.

That's what a bad driver would say.

We use automated speed cameras here in Australia, and mostly everyone adheres exactly to the speed limit. Just knowing that there could be a speed camera keeps certain people law abiding.

If you do get a fine erroneously you can contest it in traffic court.

In Australia we have automated ticket cameras and it's really not as bad as you seem to think. You literally just do the speed limit and then you have no problems. And doing the speed limit is as simple as looking at your speedometer and doing what it says. You'd be doing that anyway to make sure you weren't more than 10-15mph over, right?

Most cars have slightly different speedometers so the cameras aren't so sensitive, you can go a couple of km over with no issues.

We use automated speed cameras here in Australia, and mostly everyone adheres exactly to the speed limit

I don't live in Oz, but a recent news report would suggest it contradicts your statement. Camera revenue in NSW alone explodes as fines reach $308 million, which is than $39 million increase over last year. If your statement matched the current situation, fines would be reducing, but instead they're increasing.

Total annual revenue from speed and road safety cameras across Australia exceeds $1 billion.

Speed and red light cameras don't appear to be a traffic safety system, but instead a revenue generation channel for the state.

You had me in the first half, NGL

More state-sponsored surveillance is never the answer.

Elaborate.

I always drive at the speed limit, even if it gets me honked at. People are just impatient these days

You literally just do the speed limit and then you have no problems.

Sure, but I would like more agency than that. That’s the crux of OP’s question: is the speed limit treated as a hard rule, or a soft rule. I am on the opinion that it should be treated as a soft rule; and drivers should be able to judge the safe speed for driving that is appropriate for the road conditions, traffic, vehicle characteristics, tires, weather, driver’s experience, and so on. I don’t think that on a given road with a 65 sign, the ideal speed is 65 mph for everyone in all weather situations, in a 4wd with performance tires or a fwd with worn chinese 4 seasons tires, for a teenager who just got a permit or a commercial driver who’s been on the road at least 40 hours a week for 20 years, day or night. Maybe someone should slow down to 55 in the rain in curves, and the other guy is safe to do 70.
Why is that that folks aren’t routinely getting tickets for tailgating, for holding a phone while driving, or for drifting in and out of the lane. While you can always expect to get a ticket for speeding. It is used as a proxy of safe driving because it is easy to determine whether speed was greater than limit. But it is nowhere near being the most relevant measurement.

And the fucked up thing is: society does treat it as a soft rule in the places where I lived (many, if not most drivers go over the limit), but police occasionally set up shop and pretend we treat it as a hard rule. If you ever see that everyone is slowing down from the normal cruising speed when there’s a police car in sight, that’s a sure sign of this. The speed limit is only a hard rule when it comes to writing tickets, not when it’s about choosing the speed.

If your raise the speed limit 10-15 people will go 10-15 mph above that

Why does everyone drive 10-15 miles above the speed limit?

We don't. Some of yall do. And then you ride my ass when i don't.

Why don’t we raise the speed limit if that’s how fast everyone wants to go?

They do. Speed limits are determined by how fast people go on the roads.

Why is traffic enforcement given to very expensive and ineffective police instead of cheaper and more automated traffic cameras?

Because cameras can't beat people with batons for no reason. Also some areas do have camera enforcement.

Why do we refuse to ever use ANY traffic calming measures? Yes, than you flashing digital sign for telling me I’m going 10 miles above the limit on this incredibly wide and straight and flat road with high curbs and perfect visibility.

Your mad it's telling you you're speeding? Then go slower.

Is this Waldo on US 301?