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Almost every speed limit is too low (2017) (qz.com)
135 points by dsfyu404ed 8 days ago | hide | past | web | favorite | 203 comments





“I don’t want to lie to people,” lieutenant Megge tells us. It may make parents feel better if the speed limit on their street is 25 mph instead of 35 mph, but that sign won’t make people drive any slower. Megge prefers speed limits that both allow people to drive at a safe speed legally, and that realistically reflect traffic speeds. People shouldn’t have a false sense of safety around roads, he says."

This is likely false.

NYC changed the speed limit to 25 mph in Nov 2014. Pedestrian deaths have been sharply reduced:

1) https://ny.curbed.com/2018/1/8/16863408/nyc-vision-zero-traf...

2) https://www.nytimes.com/2018/01/08/nyregion/nyc-pedestrian-d...

At the same time pedestrian deaths in the US as a whole have increased:

https://usa.streetsblog.org/2019/03/01/pedestrian-deaths-rea...

The data is clear that lower speeds means accidents are less dangerous: https://usa.streetsblog.org/2016/05/31/3-graphs-that-explain...


You can see the Vision Zero data here: http://www.nycvzv.info/

I don't think your interpretation about speed limits is correct compared to other factors mentioned in the nytimes article:

> more stringent enforcement of moving violations, revamping hundreds of street corners to slow down turning cars and rejiggering crossing signals to give pedestrians a head start.

For one, traffic in NYC just doesn't move that fast, especially on the streets where most of the accidents happened. It's not really appropriate to extrapolate NYC data to the rest of the United States unless you focus only on urban centers.

Second, almost all of the fatalities seem to happen around intersections. I'd expect to see more jay walking deaths in the years before the speed limit change if your interpretation was correct.


>revamping hundreds of street corners to slow down turning cars

This is probably the biggest one. Lots of pedestrians and get hit by people turning right who can't see them until the last second because of other things on the street corner (like people waiting to cross in the other direction).


Also drivers who roll through a right-turn-on-red while looking the other way for cars. By the time they see the person walking, they've already slammed on the gas so they don't miss their opening.

There are a few intersections in my city that are notorious for this; I have an extremely loud airhorn on my bike that I use to blast drivers who allow their vehicle to move forward without looking where it's going.

I no longer believe RTOR can be performed safely by the majority of drivers— it should be banned.


Right turn on red has never been legal in NYC. There are specific exceptions that are always clearly marked.

Would this not also apply to right turns at stop signs? I think there is a deeper problem that needs fixing and even if we banned RTOR, it will still impact people waiting at stop signs.

Having recently been teaching someone to drive, I have strongly encouraged them to not engage in right turns unless it is clearly safe and there is no on coming traffic. Better to wait a minute than to risk hitting someone. The problem is there parents feel differently, as do the drivers waiting behind us. If people were more patient drivers, less pedestrians (and drivers) would die.


RTOR doesn't exist in France and was a source of stress when I started driving here (to not do it), and then again when back in the US (drivers honk if you don't).

My point though is that people do just fine without it.


I was almost hit when jogging through a crosswalk from this, but I saw the driver was looking left as he came rolling through the stop sign ... in his police cruiser.

That's so enraging. Honestly if I caught that on video, I would absolutely go to war to get that cop disciplined or fired, along with anyone else in uniformed who tried to defend them or pat me on the head with the usual "Hey man, relax— at least no one was hurt. Can't you let this go?"

100% agree, both as a pedestrian and as a driver. RTOR introduces deadly ambiguity in exchange for marginal convenience. It's not worth it.

I would like to be able wait for the light to change without feeling like I'm being an asshole to other drivers behind me.


New York City agrees with you.

I think left turns are the most dangerous for pedestrians, since the driver is focused entirely on timing oncoming traffic and performs the turn with a sense of urgency.

All major pedestrian intersections should be "all walks," where a period of time is established where no cars may enter the intersection.


I remember being in Japan and seeing these "all walk" signals, including crosswalks that went diagonally through the intersections. Brilliant.

I fully agree. I had two situations in the past 2 years where cars almost ran into me (as a pedestrian) doing a left turn, with screeching tires just barely avoiding me. In both of these cases I probably got out without an accident because I expect drivers to be idiots and was careful enough to act accordingly.

You summed it up when you said you expect drivers to be idiots. This is what I teach my kids. I say the cross walk does not mean a thing. One person looking at their phone and you are dead in the cross walk. I always tell them look and keep looking and expect that even if the car in front stopped be ready for the car behind him to hit him and push him into you (something that I’ve had happen personally).

The crosswalk's only purpose is to determine who pays for your funeral.

A big frustration of mine are people who used the bike lane in the wrong direction.

If you're turning right onto a road from a private residence, then you're probably only looking in the direction traffic is coming from. Someone biking the wrong way could easily be hit.


Ah yes, 'salmoning'[1]. Clearly dangerous for interactions with cars, and also a real headache for cyclists going the right direction in the bike lane - who gives way, and how?

1: https://www.npr.org/sections/health-shots/2014/05/15/3124556...


>revamping hundreds of street corners to slow down turning cars

To slow down local neighborhood traffic my neighbors put out an old single construction cone (someone has a source of heavily used cones so when they're stolen no big deal) in the middle of the road.

Folks slow down and easily drive around it. It is highly effective even when it isn't there as I suspect the local speeder folks anticipate the random construction cone might be back at anytime...


The data in your links is inconclusive. It is improbable that the 25mph speed limit, in effect for only 2 months, accounts for the drop in fatalities from 2013-2014. There were lots of other Vision Zero things happening in 2014 that likely had a bigger effect. 2015 was the first full year with the speed limit, and it looks like no real impact from 2014.

2014 (2 months of 25mph) : 140 pedestrian fatalities

2015 139 pedestrian fatalities

2016: 148 pedestrian fatalities


Came to say this. The 25 limit was set at November 2014.

There are two kinds of safety: collisions between cars and cars, and collections between cars and everything else (pedestrians, bicycles, children).

For a limited-access road or grade-separated road (especially electronic toll roads), simply minimizing the speed difference between cars is enough.

For the pedestrian case, you want to minimize the speed difference between cars and pedestrians. Speed limits are only part of a plan to accomplish this goal -- instead, you want affordances that make people naturally drive slower: removing car lanes (replacing them with trees or sidewalk or protected bike lanes), narrower lanes, adding curves to the road (but without adding blind corners), adding pedestrian crossings, and so forth.


I like this guy's take:

"The common US rule requiring speed limits to be set at 85% of actual average car speeds amounts to crowdsourcing the value of human life, on a platform where only motorists have a voice."

(https://twitter.com/humantransit/status/1123264831790899200)


I like the sentiment but I don't like that it's blatantly lying to express it. Just because I'm walking right now doesn't mean I never drive. Or the reverse.

You are missing the context of what Megge is trying to say, even though it is right there in your quote: if you want people to slow down use engineering to design a street where people will drive slower.

is there any evidence that traffic speeds have actually reduced due to the speed limit change? the vision zero project includes a whole bunch of stuff, including redesigning dangerous intersections, which the decline in pedestrian deaths could be attributed to.

Sure, it's possible that pedestrian deaths can be reduced by lower speed limits.

But in busier roadways, what I've observed is that slow drivers tend to be biggest danger now - and that is naturally because slow drivers tend to also be distracted drivers (by cellphones or otherwise). Naturally, such distraction is a bigger and bigger phenomena and dealing with them by making it clearer how they ought to drive seem OK.


Driving too slow results in more accidents.

Driving too fast results in more fatalities.

It might be nice to decrease both, but I know what I care more about reducing.


Sure but the argument is what can be controlled. The major portion of drivers are going to be driving as fast as the road allows, some portion faster and some will drive as fast they read on the sign (as they tap on their phones). We can ticket the reckless drivers, maybe have devices to reduce the average but raising the speed limit to the speed of the bulk of traffic makes sense, as per argument in article.

Kinetic energy = 1/2 m*v^2 is all I kept thinking reading this article.

[flagged]


If only it were that easy. If you think this way you're very much part of the problem. People's right to life supersedes right of way. We have to work together to accommodate each other's mistakes and reduce pointless suffering.

Perhaps what we need to do is make roadways more dangerous for motorists, so they'll slow down and not kill as many pedestrians.

Is there any data showing that people are actually driving slower in NYC as a result of the speed limit decrease?

How much of this is due to safety features to reduce pedestrian injury in accidents?

Devil's advocate, but crash fatality rates have been on a downward trend for decades.

Some safety features like automatic emergency braking, abs, stability control, and modern (more powerful) headlights protect pedestrians as well as drivers

Somewhat recently, many cars have been specifically designed to reduce injury when colliding with pedestrians, and these models have become more common in the 2014-2018 window.

I wouldn't completely discount the research, but the majority of the reduction could be that newer cars are simply safer for everyone


It's highway speeds that are too low. Street speeds are mostly OK, though the best way to fix speeding on city streets is to have speed limiting devices rather than lower speed limits.

Regarding your last link - lower speeds and lower speed limits are not the same.

Also, your claim that it’s lower speed limits that reduced deaths seems not entirely honest - the articles say that there were more things that changed besides speed limits.


There are many counter-intuitive effects in traffic engineering. Widening lanes has often been done in the name of safety, but the effect is that drivers feel safer driving faster, and the rates of deadly crashes rise.

This suggests to me that to make roads safer, we might want to design them so that drivers feel they need to drive slower and more safely. Narrow the lanes where they are too wide, add roundabouts instead of multi-level exchanges, allow tighter curves. Especially useful for cities, since these changes would give back land for non-highway uses.


On the subject of counter-intuitive effects in traffic engineering, it also seems that adding more lanes to a highway actually makes traffic flow worse. Whenever a car changes lanes on a highway, a small traffic "shockwave" propagates backwards some distance, and more lanes -> more cars crossing more lanes -> more traffic.

Anecdata: I live in DC with its notoriously bad traffic. The highways 395 and 495 have 4-6 lanes each and tons of traffic. On the other hand, the George Washington Parkway has just 2 lanes and carries a large volume of vehicles between 395 and 495, but has very little in the way of its own traffic (except in the event of an accident, of course). Traffic only really occurs on the GW at the junctions with 395 and 495 since the X95s don't have the capacity to receive all of the GW cars at-speed. Whereas the X95s will get random backups for seemingly no reason, and at all hours of the day, backups on the GW generally only occur at the ends.


Playing "Cities: Skylines" on PC and growing your small village into a metropolis will teach you a lot of things about traffic. More options for cars are usually not good for traffic flow.

The drivers in that game don't crash, and otherwise their behavior is greatly simplified, but each vehicle in that game has a start and a destination, and you can follow delivery trucks as they deliver packages and then go back to the Depot to pick up more. It's very fascinating, and may offer us some small window into the kinds of things that traffic engineers deal with without trying to find or write traffic simulation software.

And, of course, there are mods to give the player (the Mayor) greater control over lane usage and where stop signs and traffic lights are placed and how they operate. Doing things wrong will quickly result in localized gridlock.


The biggest flaw in C:S traffic flow, even with the popular traffic improvement mods, is that routes and lane choices are pre-calculated when the vehicle departs and don't really take into account alternative routes/lanes or current traffic load very well or at all. You quickly run into issues where you'll have a 3 lane road that has 99% of the cars backed up in one lane while the other 2 are wide open. Coincidentally it kind of mimics an induced demand problem, but for the wrong reasons.

Of course having every vehicle continually recalculate and optimize its path is computationally prohibitive. Given the limitations it does a pretty good job, though!


The vehicles aren't situationally aware, you're right. Nothing beyond basic "go when the car in front of you goes, and stop when they stop" kind of thing.

That said, there is a non-zero percentage of human drivers that do the same pre-calculated route and lane selection.


I found that frustrating too - all the cars piling up into one lane. I'm sure there's some stuff they could have done to pre-calculate and have some "randomness" in there to use the other lanes. There was a plugin, might still be, that kind of fixed it. Maybe I should fire it back up and see whats all new.

Isn't this how most of us operate? I almost always take the same route to work, regardless of traffic.

Route, perhaps (though I personally like to mix it up), but if the right lane of a 3-lane highway is backed up due to an offramp that isn't yours, I imagine you'd move over one lane to get past it! That's what doesn't happen in C:S, unfortunately.

You are absolutely right about the shockwaves. It is also weird that going fast and tailgating actually create slowdowns and make traffic go slower. By not leaving room to slow down, any minor lane change can cause a huge ripple of hard braking and now there is a backlog until everything accordions forward again. I wish newer cars had a constant beeping when you are 10 feet from the person in front of them at 65 mph. We'd actually see better traffic flow.

As for parkways, the better flow is because they don't allow trucks. Variance in the speed of cars is what causes traffic. Obviously this is true at on/off ramps. There is no way X95 can take two lanes of high-speed flow of cars into their already packed flow. For parkways with a lot more hills, you can still get slowdowns but these happen almost exclusively just before big hills and at exits to bigger highways (and occasionally at busy on ramps with short merge areas).


People always talk about driving with gaps[1], but I've yet to see a simulator show how detrimental/beneficial these strategies are to individual drivers.

It feels like a hawks and doves style ESS (evolutionary stable strategy) problem. It appears to me that the strategy that eliminates the overall negative affect for the group (avoid creating phantom stop signs, by gapping or "always in the middle" strategies) is necessarily unstable.

The benefit to any single driver who does not follow that rule becomes increasingly high as more and more others do follow the rule. Even to the point of ignoring a beeping car I should think. I certainly feel the negative effect driving behind someone who creates a gap as more and more cars merge in front of them. In the pathological case the driver who insists on a safe interval between cars will make no progress at all.

1: (CGP Grey) https://youtu.be/iHzzSao6ypE


You say you've observed it, but it doesn't make any sense. If you go 5mph slower than the speed of traffic, you will continuously open up a gap. You never need to slow down farther than that. The cars merging into the gap wouldn't be merging if your lane wasn't faster than their lane, so there's no reason you would have to slow down even farther. What you perceive as repeated slowing down will only happen if you sped back up to match the speed of the car in front of you after opening the gap.

I don't think you've considered what you are saying. You're not describing a gapping strategy, you're just describing a slower driver (i.e. slower traffic). There is no question that a car consistently driving slower than ambient traffic speed is a net drag on overall throughput. In any single lain of traffic all cars are bound by the slowest car. If you drive 5 mph slower than the car in front of you then the car behind you must drive 5 mph slower still to continually produce gaps behind you. As the video illustrates introducing a slower driver is one of the things that creates phantom stop signs.

Of course you must maintain speed. The point of a gap is to allow for adjustments without the hard breaking that would create a phantom stop sign. That is the overall intent of the system. Move the most people as expediently as is safe from point a to point b. The best way to do this is to avoid speed differentials, being slower then ambient traffic speed creates a speed differential.


That's not true about the second driver behind me, because people are not pulling into his gap, because his lane is going 5 mph slower than the other lanes. So he establishes it once and is fine.

This is more of a thought experiment to show that you never have to keep slowing down to zero even if for some reason people continually enter your gap. I barely observe people entering my gap at all in practice, because all lanes are generally going the same speed so there's no benefit to it.


Because you insist on the gap, your lane is 5mph slower than the other lane (because people pull in front of you after passing). Assume the other lane is doing 50 (65 mph speed limit, but there is congestion).

That lowers the throughput (number of cars that complete a trip in your lane) by ~ 10%. Also, the faster lane is now probably moving closer to your speed behind you than the 50mph you observe (because you are causing cars going 45mph to cut off cars going 50mph that lane).

The arrival rate of cars won’t change because you chose to go slow. So, if the road can handle 10,000 cars per unit time with normal congestion, it can now handle ~ 9000. That means per unit time, there are 1000 new cars sitting in the stop and go backlog that you single handedly created by creating the gap.

This has been shown time and time by traffic simulations. It only takes a small handful of slow drivers to create massive backups.

Also, the number of traffic fatalities is proportional to the difference in speed between the fastest and slowest car, so, statistically speaking, by being the slowest car, you are murdering people.


The reason I am going 5mph slower in this thought experiment is because a continuous stream of cars is merging in front of me from the other lanes. (What the OP called the 'pathological case'.) They are the reason the lane is slower, and because they are not in the other lanes, those lanes will be 10% faster.

With the pathological case being so benign, the real life experience is even better. You might get a car moving in front of you once a minute, and usually a few seconds of slower accelerating or coasting is all you need.

To me the thing that really slows down traffic is people not moving left to let onramps merge. I think that's because they are afraid of missing their exit because no one is leaving gaps.


> I wish newer cars had a constant beeping when you are 10 feet from the person in front of them at 65 mph. We'd actually see better traffic flow.

I just drove a Ford Edge that had this. It is a little overeager about what it thinks is an impending collision, but it works alright.

The adaptive cruise control is a mess though. In theory, it is supposed to match your speed to the vehicle ahead if they are slower, so you don't have to pay attention. In practoce, it has the potential to be a great contributor to congestion. With dumb cruise control, you can push slowpokes to get out of the way or at least speed up; the adaptive cruise control seems to match speed at a distance where the driver ahead doesn't get the signal that they are obstructing things, and they continue bumbling along.


For highly congested areas the increase in the number of lanes is done to accommodate the number of cars on a given route (optimize for capacity). If you can physically fit four times as many cars on a route, but it results in only being able to move at 1/3 normal speed you are still moving more cars over time than a two lane road.

It's not random, it's poorly engineered entrance and exit ramps. In order to maintain traffic flow, cars need to be able to increase to traffic speeds on on-ramps and decrease on off-ramps. Much have the beltway system put entrance and exit ramps where they definitely don't belong. Thoroughfares for in-city traffic also don't exist, the interstate has taken that role. To compound the problem, often times entrance and exit ramps are the same piece of pavement.

I think a lot of the counter-intuitive effects in traffic engineering are due to traffic arbitrage. If you make a path much better more people will take it until it's as bad as all the alternate routes.

It can actually be worse. This is called Braess's paradox [1]. The relevant part is: "an extension of the road network may cause a redistribution of the traffic that results in longer individual running times."

Further down in the Wikipedia article is an actual example.

[1] https://en.wikipedia.org/wiki/Braess%27s_paradox


If a lane is shut down due to an accident, it is better to have five spares though.

> This suggests to me that to make roads safer, we might want to design them so that drivers feel they need to drive slower and more safely.

Yes: https://en.wikipedia.org/wiki/Traffic_calming


I read an article long ago about incorporating optical illusions into traffic calming. Things like the shape of ditches and the placement of trees on highways and parkways to make the shoulders look narrower than they really are.

Making the road appear more dangerous than it really is makes people slow down and pay attention, without the uptick in danger of an actual hazard.


"Let's train people to ignore danger"

what we need is red camera* at every light and speed trap at every road, only the fear of enforcement keep people honest

*minus the whole shorten yellows for profit, of course


Surely we could more or less eliminate all kind of law violations by total control. But I don't think this is what we want as a society.

I'm not arguing about every single law, only those that have impact on the leading cause of death beyond health issues in the civilized world

but ok, nice slippery slope, I guess.


Let my rephrase it in a better way I hope.

I'm not trying to say that once we introduce methods to fully detect some types of law infractions it will inevitably lead to a totalitarian regime.

But I believe some leeway is necessary for people to feel comfortable and somewhat free. I don't want to be punished every time I make a mistake. I think you can find some sweet spot between zero and total detection. And yeah, probably leaning towards the latter, in correlation with seriousness of a violation (optimal discoverability reaching zero rather means the law should be revoked, like jaywalking being penalized in my country imho).

Also, how would you even know some law is optimal when no one violates it? I mean, we could put radars on every road and set the limit on 30 kph. The studies discussed in the article wouldn't be possible then.

> I'm not arguing about every single law, only those that have impact on the leading cause of death beyond health issues in the civilized world

Definitely speed is the factor. But what about other variables at play like road quality, intersections planning, lights, other traffic regulations? And if tweaking them actually lowered casualties equally well with better economical outcome?

> only the fear of enforcement keep people honest

As for a slippery slope. You vastly generalized your statement yourself tbh.


Similar to a phenomenon in sports - more and better protective gear leading to more aggressive play leading to more injuries instead of the expected less.


> This suggests to me that to make roads safer, we might want to design them so that drivers feel they need to drive slower and more safely. Narrow the lanes where they are too wide

anecdote about the opposite happening:

There is the I90 tunnel in Seattle which I use very often. Some passages have 2 lanes, super narrow, no shoulder, nothing. Looks like this: https://goo.gl/maps/DzvhWZAoD5AkRVwA9

You won't believe how fast people are going through that. Also, almost every time I get tailgated and I'm frankly amazed there hasn't been any major accidents in that tunnel considering how close people are driving (no following distance). Just yesterday I was tailgated by somebody on their phone (I could see the screen reflected in his face while he was texting). I don't want to imagine how an accident would look like in that tunnel. Honestly, a fender bender can become catastrophic before you realize what happened.

Now if you mean 'narrowing' roads then probably yeah. Take a wide-ass lane and suddenly make it narrow (so that people using it every day are 'surprised' and they're more careful) and I could agree with you.


More like unintuitive rather than counterintuitive, because the prediction doesn't fail because wider lanes are more dangerous per se, but because of the behavioral response of the drivers. Which can actually be considered "intuitive" to someone who is used to trying to model such things.

Where I live in the south of Germany nearly every residential area has these artificially narrowed roads and it works a lot better than putting up a incongruent signs ie 30 on a 50 looking road.

It also can look pretty nice when they use flower beds and trees for the narrowing:

http://www.ibfunk.de/ibfunk-wAssets/img/leistungen/verkehrsa...


I enjoyed the survey that the book _Traffic_ by Tom Vanderbilt provided in the traffic engineering space.

Many of the topics discussed in the comments I see here are discussed in the book.


I don't know how many time roundabouts and gps have caused near dangerous split attention that just does not happen with normal stoplights. They may be better for local traffic but for anybody from out of town they are worse.

>Roundabouts reduced injury crashes by 75 percent at intersections where stop signs or signals were previously used for traffic control, according to a study by the Insurance Institute for Highway Safety (IIHS)

https://www.wsdot.wa.gov/Safety/roundabouts/benefits.htm


Accidents happen at intersections because many drivers are not good at making themselves aware of traffic approaching from multiple directions. At a roundabout drivers only need to look in one direction. They are strictly better than traffic lights for all drivers except those who are not experienced with roundabouts. Those drivers should familiarize themselves with roundabouts.

Of course it's always possible to screw up a good thing: the intersection next to our house has been replaced by a roundabout with a 2-way stop sign. To make it worse, you can really only see the traffic coming from one of the other 2 directions when you are stopped.

Result (people not being familiar with roundabouts doesn't help): people stop in the middle of going around the roundabout, and/or get honked at by the people coming from the 2 directions without stop signs. I'm sure an accident is coming soon :(


this sounds like some traffic calming measures that were recently installed near me just last year

they are islands in the middle of the intersection, but not roundabouts, forcing cars to "swerve" to pass through

they haven't worked as intended and are being re-evaluated


Roundabouts are better for car-car crashes: there are fewer of them and they tend to be less serious— rear-enders where there's lots of crumple protection instead of T-bones like a conventional intersection.

However, they're much, much worse for people walking and cycling.


I agree that roundabouts and sidewalks do not interact well. Cyclists should take the entire lane in a roundabout, because otherwise cars will not notice them. Pedestrians should be very careful.


There's definitely a design component there, but I do wonder how much of it is in culture and enforcement (which can change the culture over time).

For example, the roundabouts in my city (Kitchener ON) all have a sidewalk or multi-use trail crossing each vehicle entrance and exit, and without fail, every single crossing is marked with a paint ladder, stopping teeth, and a "Yield to Pedestrians" sign. I've also confirmed with city engineers and law enforcement that people walking are supposed to have right of way at these crossings— like, you're waiting to cross, and drivers see you and stop, and remain stopped until you're fully off the roadway.

But it's not like that at all. I have dozens of helmet cam videos of me walking my bike through these crossings and being buzzed by cars who don't see me at all, or don't see me until it's too late, or see me but don't think they need to stop for me. I send these videos (many with clearly visible license plate numbers) to the local media and contacts I have at regional police, and I get a collective shrug back.

I met with city engineers in the winter to ask whether they thought it was safe, and they said that yield compliance to roundabout crosswalks was 70-90%. They said this like it was a good thing. Literally one in ten cars doesn't stop for a person walking in a marked crosswalk, and that's somehow acceptable.

I'm not sure how to change a culture, but camping some cruisers there for a week and handing out a few hundred tickets for $1000 each [1] to non-yielding drivers sure would be a great start.

[1]: http://www.mto.gov.on.ca/english/safety/pedestrian-safety.sh...


Lived in the UK most of my life, roundabouts and walking/cycling was never a problem more than crossroads. Don't know what you're on about.

One of the fundamental advantages about roundabouts is that even when crashes do occur (and all the studies show they happen less frequently), they're less likely to be fatal. Instead of being t-boned, with at least one of the vehicles driving at speed, you're getting either side swiped or rear-ended, which is safer for all drivers involved.

I miss roundabouts whenever I drive in North America. I'm not used to intersections (which could be the problem) but it seems like you have to look everywhere as opposed to just looking in the direction traffic is coming from.

Could put a big spike on the steering wheel

Given this article's argument (the speed of traffic is largely independent of the speed limit, and depends more on the road itself), the logical path to decreasing road speeds is https://en.wikipedia.org/wiki/Traffic_calming. In my experience, California residential streets are especially egregiously bad in road design, having wide streets (often approaching 2 full lanes per direction, although the outer "lane" is unmarked and used for street parking) that suggest a speed 15 mph or so greater than the speed limit.

That is 100% correct.

If you build a 50 MPH road through a neighborhood, you're going to get 50 MPH traffic through a neighborhood.

What the signs say is irrelevant unless there's a cop right there.

If you want slow traffic, build slow roads.

Likewise, if you build your house on a fast road, don't expect traffic to slow down just because your kids are there.


traffic calming measures in residential streets have so many benefits. bulb-outs not only slow traffic, they reduce pedestrian crossing distances. street trees slow traffic by making the street seem visually narrower to drivers without actually narrowing the street, and also create shade, improve property values, and regulate temperature.

Until the ladder truck can't negotiate the corner.

People downvoting this need to learn from history. The Oakland Hills fire[0] was made far more lethal than it should have been because the narrow, vehicle-clogged roads prevented fire trucks from ascending the hills.

[0] https://en.wikipedia.org/wiki/Oakland_firestorm_of_1991


It‘s worth noting that Europe has lots of small winding roads and is not noticeably more dangerous in terms of fire safety.

In fact, what has happened is that average fire truck size in the US is much larger than in Europe, and that is what drives the requirement for wider streets. https://www.citylab.com/transportation/2018/12/fire-trucks-e...


Or the subdivision I used to live in where right before they moved the city hall across the street they tore-up the landscaping in the middle of the entrance and bulges on the sides near intersections for this reason. For a few years it was this way, fortunately there was no fire in the meantime. They added more speed humps in the process.

Where the obvious solution is to build less obscenely oversized firefighting vehicles.

I agree traffic calming is a very useful tool in making streets safe, but I also want to bring attention to this picture found in the gallery of that page and how it relates to the basis of the original article.

https://en.wikipedia.org/wiki/Traffic_calming#/media/File:Di...


Interesting to read about that percentile design. Here in Germany we have (as you probably know) a few hundreds of kms of unlimited Autobahn (advised is 130kph). These roads are way better and safer than the US highways and freeways I experienced, btw.. So it is not a fair comparison.

Nevertheless we have a heated debate were many very loud votes in the media demand a speed limit of 120 or even 100kph. Because that is obviously necessary and everything else is stupid.

Now, while there are certainly many more or less valid arguments for a speed limit, I have never heard anyone arguing about the number. The verocity of the debate is contrasted by a total lack of arguments for or against a specific limit. Why 120 and not 130 or 90. What about 160?

To me it looks like there are many people either offended by or incapable of dealing with other people making different choices. The whole debate seems to be a way to force others into coercion and the actual limit is chosen to coerce as many people as possible.

So in Germany the debate seems to target at the complete opposite to define a speed limit at the 15th percentile. That's an intriguing observation. And rather typical for us, tbh.


Germany also has much higher standards for driver education, stiffer fines for infractions, and a safety first approach towards operating heavy machinery. In the US, you can get a license by answering 25 questions, driving around a block, and doing some sort of parallel parking exercise. They pretty much hand them out regardless of actual driving ability.

One thing that would reduce the number of crashes in the US is making tailgating and passing lane camping a heavy infraction. To drive safely is to anticipate conditions and expectations.

I would also support 10 year renewal testing before age 65, as bad habits quickly become routine. Shorter intervals thereafter.


We have to make the USA a viable place to live without a vehicle before we can increase license requirements. If we raise the standards too high, then people will just drive without licenses. Of course, it's probably a self-correcting problem, because I suspect many poor drivers are doing so out of obligation and would no drive if they had a viable alternative.

Designing our cities around the automobile was one of the worst mistakes this country made.


Also of note is that it's illegal to pass on the right in Germany, making traffic more predictable and orderly.

It's illegal in the US as well, just hardly ever enforced here.

It depends on which US state you're in.

Germany also has much higher standards for the engineering of the actual roads themselves.

Like, they are designed to function 24x7x365 for years and decades on end, because they have a much deeper and thicker roadbed, and much better irrigation and runoff control.

Part of this is because the road maintenance costs are built into the initial build cost, and any further maintenance in the future has to be done for free, at the cost of the road builder. And to the standards required by law. Since no road builder wants to ever have to pay for any future repairs, they seriously engineer the heck out of the roads to begin with.

Here in the US, repairs to roads are a profit center. So, of course road builders are going to make them as cheap and cheesy as possible, so that they can cash in on all that great guaranteed future income from all the repairs they're going to have to make in the next few weeks, months, and years.


I think a big source of contention is a failure to clarify what type of road requires change, leading to frustration from people believe someone wants to drop their suburban 45mph artery road with no driveway access to 20, when the other person is just talking about an collector in some dense urban zone. Not to say those people may have a point however; speed cameras always seem to have a mysterious way of appearing on split expressways with a new speed limit rather than the avenue near the school zone that actually requires it.

I've driven the unlimited Autobahn and saw no significant difference in driver behavior from what I'm used to here on the east coast US. If anything, it felt like trying to drive in Miami where you've got both hotshots driving way too fast in anything they can get their hands on (even if the suspension, downforce, and brakes aren't designed for it) and old Grandma's driving way too slow in cars that won't be able to keep up with fast traffic.

> Now, while there are certainly many more or less valid arguments for a speed limit, I have never heard anyone arguing about the number. The verocity of the debate is contrasted by a total lack of arguments for or against a specific limit. Why 120 and not 130 or 90. What about 160?

You could ask the same question for basically every other limit. Why is the speed limit in cities usually 50 and not 40 or 60? Why do you need to be at least 18 years old to have the right vote, why not 17 or 19, ...?

In the end most of those limits aren't determined by a single argument but by many. Speed limits have to take into account the road quality, the traffic density, the kind of vehicles sharing the same road, how many pedestrians are around, environmental aspects like wind speeds, ... You also don't want vehicles with huge differences in speed.

The later is my favorite argument against the missing speed limit on parts of the German Autobahn. You can have everything between stopped vehicles in a traffic jam, a tractor with 60km/h, trucks at 100km/h or less when they struggle with inclines, the average cars at around 130km/h, the business people rushing from one place to the other at 160-220km/h and those who just like to have some fun with their sports cars or bikes at >200km/h with no limit.

Of course I have no idea what the best limit should be in every case, instead I suggest to figure this out with lots of experiments. Introduce certain speed limits on certain parts and find out what an effect this has on the number of accidents, traffic jams, efficiency, noise, etc... Then the speed limit can be adapted according to those results.


>To me it looks like there are many people either offended by or incapable of dealing with other people making different choices. The whole debate seems to be a way to force others into coercion and the actual limit is chosen to coerce as many people as possible.

This observation applies to a hell of a lot of things.


> "This is why getting slow drivers to stick to the right lane is so important to roadway safety; we generally focus on joyriders’ ability to cause accidents—and rightly so—but a car driving under the speed limit in the left (passing) lane of a highway is almost as dangerous."

i really wish people would heed this rule about slower cars staying to the right (regadless of speed). if you are not passing the car to your right, you should move to the right until you are, but many people scoot to the left lane and set their cruise control so they can zone out (and possibly occupy their brains with something else like talking to other people).

this would not only minimize speed deltas and reduce accidents, but it would also improve throughput as speedier traffic clears out faster. and drivers should never just zone out while operating a machine capable of killing people.

in any case, i both agree with the article--i actually think speed limits should be accurately set at the 85th percentile, called "suggested speed" or the like, and decriminalized--and support traffic calming measures in urban areas like narrowing lanes, adding more trees/curves, and making commercial streets mixed use by default.


While currently living in CA and having driven in many foreign countries - predominately France, sticking to the appropriate lane makes a HUGE difference, from personal experience.

French drivers will mercilessly tailgate and flash their lights at you if you're driving too slow on multi-lane roads. They live by the rule to be as far to the right as your preferred top speed allows, no matter your actual speed in KPH or the speed limit, so that faster cars can be on the left. (How it is supposed to work in the states.)

Even if you're doing an easy 145KPH (90 MPH) and you're in the far left lane and another car is approaching faster, you are 100% expected to move to the right and allow them to maintain their illegal speed. I absolutely love their driving behavior.


I think the "Slower Traffic Keep Right" signs may encourage noncompliance because nobody wants to think of themselves as "Slower." Perhaps a better sign would be "If a car passes you on the right, YOU get the ticket."

Germany's rule is to stay as far right as possible as long as you don't need to overtake any cars or there aren't any cars ahead of you that are slower than you. It has nothing to do with how slow you are, but everything to do with traffic around you.

That's why the signs should use the alternate phrasing "Keep right except to pass". Usually, I only see these on two lane highways.

Alternatively, "keep left lane open for passing", which I have seen on overhead electronic signs on 400-series freeways in Ontario.


some drivers think it's their right to drive the speed limit in the far inside lane and want others to obey the law

Sometimes I ride with those people and ask them "Are you a cop?" They are always shocked to discover that without a badge they have no legal right to enforce speed limits.

Many people also dont want to be considered unnecessarily fast or aggressive.

Marines notwithstanding, people tend to be okay with being slower in the high desert area of Southern California.


That doesn't make any logical sense. If you're driving the speed limit and some idiot is 20mph above it he can switch to the right lane far faster than you can and often basically cuts you off from behind. If you decide to switch to the right too then the situation is reserved and you're cutting them off which massively increases the risk of a collision. Your solution will just result in more people driving above the speed limit or more aggressive driving to protect the right lane. Ticketing people because others broke the law is completely insane.

If you had not been hogging the left lane you would not have been in that situation to begin with. Hence you deserve a ticket.

There is a single 6 lane highway going through the town I live. From slowest to fastest the lanes are: Middle, Left, Right.

What happens is all the slow traffic (-5 to +2 of speed limit) doesn't want to deal with the absurd number of on-ramps (12 in 13 miles!) so they move to the middle lane. Then the moderately faster cars (+2 to +7 of the speed limit) pass on the left. Then you get all the people that want to go faster and they go to the right lane and then cut across to the left when cars are merging.


As a slower-than-average driver, this is exactly what I do on any highway except an interstate.

My logic is that if there are 3 or more lanes, the furthest right lane should be for getting on or off only, further left is for fast long-distance driving, and the slowest lane should be second-from-the-right.

I do not see how it makes sense to encourage slower drivers to take the far right lane in this scenario. It is actually pretty dangerous for people trying to merge on to have the right lane heavily occupied.

However, indeed the counterargument is that this leads to a lot of lane swapping when people get on and want to cross over to the far left to travel, and then all the way back over to the right when they want to get off. Especially since speed of travel is not necessarily related to whether the car is making a short or long trip on the highway.

The real question, I think, is what should a fast driver do if they get onto a highway, and are planning to get off in 1-2 miles. Should they bother crossing over to the left or stay in the right lane?


If you're going the same speed as the lane, it doesn't matter how busy it is as long as there's a car sized gap. If you're coming to a full stop and then trying to merge with a moving lane (what you shouldn't do), then yes, the busy lane is much more dangerous.

But if you're trying to merge on, whether or not you have to stop before merging is not totally in your control. Specifically, if the right lane is packed, you may have to stop if there is no opening as you pull up. Then it will be harder to merge in, not only because you are starting from zero velocity but also because the lane is packed.

That is why I think people should not get in the right lane on a highway unless they are about to get off.


Don't stop if the right lane is packed. Keep going and a gap will open as traffic accelerates away from the stopped group creating distance - you don't need to merge immediately.

I don't see how it's more dangerous to have cars merging into the slowest lane than to have cars merging into the fastest lane.

yes, in california we also have drivers who sit in the middle lanes ignoring the surrounding traffic conditions (which is totally fine if traffic is light, or very heavy since everyone is stuck doing the same speed). and so similarly, the right lane is often the fastest lane, which, on city streets, raises the overall danger (particularly to pedestrians and cyclists).

although i believe the biggest cause of accidents is distracted driving (which is hard to correct, short of culture change), i'd still support raising the overall technical skill of driving in the population through a variety of means: more training (defensive and offensive driving), simulation (video games? competitions?), stricter testing, differential licensing, etc. maybe then everyone would know how to speed up and slow down to merge properly and the right lane wouldn't be so unnatractive.


I wonder if there's an unfortunate thing going on where it's not really about the number posted, it's about going faster than the people around you.

Driving is a lot easier and less stressful if you're going faster than everyone else. You really only have to worry about the stuff in front of you that you see all the time, and as soon as you pass someone they are no longer a concern.

Similarly it takes a lot more attention if everyone is going faster than you. So there's always an incentive for each individual to speed up a little.


I think you're giving people way too much credit. Most people aren't paying attention to traffic behind and beside them even when they're the slow car.

I find it's the opposite - when you're traveling faster than the average, you are constantly adjusting your speed or having to change langes, as you come up on traffic from behind. You also get frustrated at nearly every car that slows your progress, especially if they're blocking all lanes.

If you're going slightly slower, you can just stay in your lane and cruise. Cars occasionally pass you, but that's it. It's way less stressful.

Plus there's always someone going faster than you, no matter how fast you go.


This comment got downvoted to dead? It's just what I was going to say! Driving slower than everyone else is the closest thing you can get to autopilot.

Is this whole article premised on this one guy's intuition that speeding must be safe because we aren't all dead?

There are actual studies on this stuff based on the changes in U.S. federal speed limit rules in the 70s and then again in the 90s. They are not conclusive but do suggest that higher speed limits lead to more fatalities: https://en.wikipedia.org/wiki/National_Maximum_Speed_Law#Saf...


Those studies are useless when compared to literal death rates in roads with higher speed limits.

More people died in Montana after they were forced to put real speed limits on the roads, with police enforcement: https://www.motorists.org/press/montana-no-speed-limit-safet...

The German autobahns are extremely safe compared to their other roads. The US interstate system can easily support "Reasonable speed limits" on most of their roads - its flat and straight.

These studies don't take into consideration what actually happens when some people decide to follow the law and some people decide to travel at the road's natural speed. That delta is the cause of so many accidents.


Today's cars are much safer than the cars of the 70s at higher speeds. Not only do they better protect the occupants in an impact but they steer better, break better and are far more stable. Add to that better fuel efficiencies and it's hard to argue that we need the same speed limits.

55 was a response to the oil crisis but it also reflected automobile engineering of the time.


Yes, they're much safer for the occupants. They're probably less safe for pedestrians and cyclists hit by them, considering the increase in mass and height.

> considering the increase in mass and height.

Most of today's cars are significantly less massive even if their size is larger.


My first car was an '84 Ford Crown Vic LTD, that beautiful monstrosity of a two door coupe. It was ~215 inches long and was made out of ~3650 lbs of Detroit steel. I now drive a 2015 Ford Escape, which is 178 inches long and weighs ~3550 pounds.

Similar-sized cars are probably lighter nowadays, but the overwhelming shift towards SUVs holds back the average mass.

Now I'm misty-eyed, thinking of my beautiful LTD... a completely inappropriate car in 2019, but so much fun to drive.


Every new car is designed with pedestrian safety as a concern. Pedestrian safety regulations are the major reason all cars share the same profile. Designers don't have much leeway when it comes to the shape of a car because all the panels need sufficient cushion and be angled such that pedestrians are deflected, and there's only so many ways to accomplish that. So designers focus on what they can change, which is pretty much grills, tail lights and door creases.

I am sure there are design considerations, but the IIHS believes there’s a link between rising pedestrian deaths and the rising proportion of cars on the road being SUVs. Source: https://usa.streetsblog.org/2018/05/09/study-links-rise-of-s...

I have a 2010 model car and I still seem to get significantly better gas mileage around 55-65 mph than I do around 70-75, although I haven’t measured it scientifically.

Isn’t this a function of wind resistance physics that can’t be solved, just mitigated?

As driving automation increases and the threat of climate change and CO2 emissions looms larger, automated cars could drive at current speed limits without getting impatient like a human driver, improving both efficiency and safety.


   Isn’t this a function of wind resistance physics that can’t be solved, just mitigated?
Yes, this is fundamental; roughly power required is proportional to cubed velocity. Improved coeff of friction helps, but you can't get away from this.

Eventually air friction is the completely dominant force. So at highway speeds, absent some rare gearing issues causing inefficient fueling, faster means less efficient.

This is also why the fastest "hypercars" are pushing on order of 1000 hp.

At lower speeds, all sorts of other issues kick in (and idling is its own issue)


A demonstration of this fact can be found in a list of fastest production cars in the world:

https://en.wikipedia.org/wiki/Production_car_speed_record

The RUF (Porsche) needs 460hp to break 213mph. The next record breaker needs 618hp to break 221mph. The 241mph record is made with 806hp. This continues incrementally until the current record holder, which needs 1350hp to hit 278mph.

It took three times as much power and three decades of computational advancement to build a car that could go a mere 65mph faster than the 1983 record breaker.

Side note: the listed horsepower numbers before 1980s are basically made up. You can safely assume SAE J2723 horsepower (what cars use today) is ~60-75% of published value for cars older than 1980 (and about ~80-95% for cars between 1980 and 2005).


It does. Almost any car will be more efficient around 50-60mph.

But it only matters on highway where the bottleneck is due to aerodynamism, at lower speed you might be less efficient at 20mph than 30mph for example.

https://en.m.wikipedia.org/wiki/Fuel_economy_in_automobiles


It's a bit of both but yes velocity dominates the drag forces. You can reduce the wind resistance of vehicles reducing their coefficient of drag but the dominant factor as you reach higher speeds is velocity which increases as a square where the drag coefficient is only directly proportional to the end drag. There are definitely limits to how low drag we can make the normal passenger sedan without drastically changing it's functional form.

If we move to a more infrastructure style car transport where you just subscribe or have access to (depending on where we end up on the public-private spectrum) there's probably a lot of gains we can still make that will make cars much uglier (to our current eyes) but more aerodynamic.


OTOH, during the 70s drunk driving, heavy smoking, not using seatbelts and a whole host of other very dangerous activities were socially acceptable.

A bit of pedantry, but I see it a lot on HN. You definitely do not want your car to break. You may want it to brake.

I dunno.

If I hit a hard barrier, I'd prefer that the car break and disintegrate and dissipate all that energy, as opposed to transferring all that energy into me as the occupant.


I am all for raising the speed limit if the speed limit is lower than what is safe, but I have an issue with the way the article blames drivers who drive at the speed limit for the delta in speeds. If we all need to agree on a speed to drive, why not choose the one that we can drive at without risking being pulled over and ticketed?

The ticket isn't actually one for traffic safety, even though that's what they'll call it. If it were actually unsafe you'd expect far more crashes based on how often everyone drives "over the speed limit".

The reality is that "being tough on crime" and "doing something" are political points, and the use of a ticket system generates revenue. If it were law that all funds related to minor traffic infractions had to be donated to charity (without counting for taxes) you'd see a MAJOR decrease in enforcement.


Because a road has a natural speed, and that's what most people will drive at when they're not actively thinking about it.

If the speed limit is below that natural speed, you end up with most drivers going faster while the few follow the absurd rule.


The problem is that the "natural speed" for a road is based on a human brain's subconscious calculation. And the human brain is very bad at doing that for any speed faster than a good runner can go.

Actually the human brain is good at finding the natural speed. Many roads have a natural speed that is higher than the safe speed and this is a problem. When the road itself says drive some speed the human brain is not good at reading that the road is tricking it and the safe speed is slower.

The above is a failure of engineering. It has been well studied in academics, but few actually account for it.


Is it absurd to not want to get pulled over?

I'm not arguing against raising the speed limit to the natural speed. I'm against blaming (and tailgating and generally harassing) drivers who are following the speed limit because they don't want to have to pay a fine. It seems like the blame is misplaced.


> why not choose the one that we can drive at without risking being pulled over and ticketed?

Usually because the perceived (and even the actual) danger of driving at higher speeds is minimal. A great example that I've seen is an access-controlled highway built to modern safety standards limited to 55mph, when the highway is designed to safely support upwards of 80mph.

More, increased speeds increase the carrying capacity of a highway; that is, more cars can utilize the highway in a given time period - like rush hour.


I'd be curious to see how much increased speeds increase capacity if people actually maintained a safe following distance.

The rule of thumb is to stay ~2 seconds behind the car in front, which means the distance obviously increases linearly with speed. If you're 75 feet back at 30mph, you should be 150ft back at 60mph.


Actually the time-to-0 increases linearly with speed, but the distance required increases quadratically with speed. If you're 75 feet back at 30mph (this seems overly cautious?), you should be 300 feet back at 60mph.

Basically to go from 60-55, 55-50, etc. takes the same amount of time, but you're traveling faster and therefore covering more distance throughout the course of the former intervals than the latter ones.


"It's too slow"

In Berlin (I don't know if it's different in other parts of Germany) and in Poland the default speed limit in cities is 50kph (~30mph). In Berlin most drivers match speed limits. In Poland most drivers ride at 70kph (~45mph) in cities. But Berlin drivers will drive above speed limits when there is a short section with construction, when nothing apparent is happening on it. Maybe they will take the feet out of gas. But most are not riding with 30kph (~20mph) speed limit in this case.

Reasons for the discrepancy between Berlin and Poland is in mentality for sure. But I think that more roads are really set for the speed limit in Berlin than in Polish cities I know. So you can drive faster, but you will just be first on the red light. As they say: slow is smooth and smooth is fast.

It certainly helps that the Autobahn network have nice stretches without speed limits. I feel that car in Berlin is really just to go to the highway and not to move through the city itself. The limits just picture the priority of public transport and bicycles in city planning.

What's funny is that I like to drive more in Berlin than in Poland. It's smoother and drivers seem more used to interruptions. Even though I still drive more in Poland and don't really need a car in Berlin. However parking is pain in whichever country I am.


"It may make parents feel better if the speed limit on their street is 25 mph instead of 35 mph, but that sign won’t make people drive any slower"

Just changing the sign doesn't make people drive slower, but if you actually enforced those speed limits people would slow down and pedestrians would stop dying. Traffic calming may be a cheaper way of slowing people down than enforcement.


The article mentions that the 55mph speed limit was pushed by the Federal Government during the 1973 oil crisis to reduce gas consumption...

...but doesn't take the next step to point out that in our era of reducing climate emissions it might make sense to drive a little slower if you're not in a hurry to get there.

Owning an electric car makes it very obvious how much smaller your range is when you drive 70-75mph than it is when you drive 50-55mph.

I'm sure people will respond to point out that these kinds of individual choices about behavior are noise in the fight against climate change. But maybe you're arguing for a renewed 55mph speed limit, then?


> Owning an electric car makes it very obvious how much smaller your range is when you drive 70-75mph than it is when you drive 50-55mph.

I got optimal fuel consumption in my Acura CL at an average speed of about 65 MPH. That maximal efficiency point varies from vehicle to vehicle, particularly across different vehicle classes.


I've heard that idea for a long time and have wondered about it: drag (air resistance) is dependent on the square of the velocity and in highway cruising where you're not accelerating, overcoming drag is a huge part of energy expended. How can the engine be tuned to be so inefficient at lower speeds that it somehow gets better fuel efficiency at higher speeds? And if that was ever a thing with older engines, is it still a thing with modern fuel-injected engines that sense performance and adjust fuel injection to optimize?

Driving slow in the left lane is a problem. Driving slow in the right lane doesn't seem to be a bit problem. Germany has sections of the autobahn with very large speed variances, but they are aggressive about enforcing the slower traffic keep right rules so fatalities low.

There are more reasons to control speed than safety. As the article mentions, Nixon lowered speeds to reduce fuel consumption in the US. Considering the climate crisis, I think that's a motivating reason to have lower speed limits.

But as others have mentioned the means of getting people to drive slower or more safely or more efficiently may not be limited to the numbers on the sign.


I am from Brazil, that for some reason unknown to me went along USA speed limits.

I started driving more or less recently and my town has several speedtraps, and they make me unsafer, becuase I am not used to driving a lot yet, I tend to respect speed limit all times, because I don't know where the speedtraps are, this has some consequences:

1. LOTS of honking when I am 5kph slower than the limit...

2. Because of the point 1, I tend to stick to the limit, this mean I am often looking at my speedometer instead of the road, and almost crashed because of this more than once.

3. Often I am overtaken in ridiculously crazy ways, like people overtaking in the opposite direction lane, or during corners, or more than once motorbikes overtaking me using the gutter, passing between my car and the sidewalk.

4. Also a couple times I almost crashed on the rear of experienced drivers that were speeding and I don't noticed, andwent along with the flow, only for them to suddenly slam on brakes right before the speedtraps (only to just as suddenly accelerate again right after them).

5. Often lanes end with strange speed discrepancies, sometimes in unsafe situations, for example there is a one-way road in my town that is in a steep hill that has a curve toward the right, often the left lane is full of people trying to overtake the entire right lane that is following speed limit, and the railings on the outer side of that curve are full of marks of people grinding on them.

I've seen once a group of 10 or so cars that were speeding slightly try to overtake a car that was following speed limit only for the first one of the group to crash on the rear of a bus that was on a bus stop when he tried to overtake from the right side (the other 9 or so cars squeezed themselves between the crash and the cars that stopped on the left lane while braking... lots of screeching).


Previous discussions:

https://news.ycombinator.com/item?id=14196812 (2 years ago, 725 comments)

https://news.ycombinator.com/item?id=8133103 (5 years ago, 207 comments)


Speed limits in pedestrian-heavy urban areas and children-heavy residential areas absolutely have to be no more than 25mph. The difference in survivability stats for pedestrians struck at 25 vs 35 are stark. What we need are narrower roads, pedestrian islands at intersections, and harsh enforcement.

On highways, it doesn't matter. Survivability between 65 and 75 or even 85 is not that much different. You're going to have a really bad day regardless of speed. Far more important is longer ramps, higher vehicle inspection standards, and higher licensing standards. We also need to get long-haul shipping off the roads and back on the rails.


It isn't speed limits, it is road design. A well designed road would ensure residential streets wouldn't be driven at faster than 25mph, no enforcement needed.

Highway speed still matters for reaction and braking distance.

Speed limits are set deliberately low so that police departments can collect fines whenever they need to buy a new cruiser.

This. Speeding kills, your pocketbook.

https://youtu.be/2BKdbxX1pDw


Part of the issue is that the speed limit often times dictates how the street is designed.

In my city, the default speed limit for city streets was 30mph. Safety advocates lobbied for and achieved lowering that limit to 25mph.

The goal was not that cars would immediately all start driving 5mph slower, but rather to direct the city's traffic engineers to start designing the street layout to lower the 85th percentile speed by about from 30mph to 25mph.


Ten years ago I would find articles and blog posts about how awful the speeders and tailgaters are in portland. The blog would effectively blame the influx of Californians.

Today (and this started about 4 years ago) you do the same search in google and you only find articles about how slow some people drive in Portland and that they are a nuisance to be removed.


Former Californians now outnumber everybody else I guess.

I'm certain that in at least some cases, speed limits are kept artificially low so officers have an easy reason to pull someone over. This is done to give officers an opportunity to inspect you for other violations.

I'm also certain that if one day every driver made nothing but legal driving maneuvers, the world would shut down before lunch.


"Speeding and traffic safety have a small correlation."

You know what doesn't have a _small_ correlation? Speeding and efficiency. Above 60mph almost any car lose an insane amount of efficiency due to aerodynamic drag.

I'm all for raising the speed limit but we should get rid of ICE before doing so.


I live in Texas near SH 130 which is (in)famous for having the highest speed limit posted in the nation (85mph) I think only on the Autobahn can you legally go faster anywhere in the world. In the end you have the normal rabble rousing in the news cycle whenever there is a fatal crash (anecdotally uncommon) but would love to see some statistics comparing SH130 Crashes and fatality rates to other roads in US or world. Some cursory googling does not reveal any studies of this caliber unfortunately.

Thats is an odd article seemingly based on an informal rule applied when revising limits and the officer's personal perception/experience. It even cites scientific evidence to the contrary but simply dismisses it by pointing to the personal experience of the expert.

Here's a personal experience: driving in Belgium, the Netherlands or any other country with limits is much more pleasant than driving on German motorways, where you have 40-50% of roads with no limit whatsoever. The high limit means even as drivers tend to be much better trained than in most other countries I've driven, German traffic is unpredictable. You'll overtake a truck driving 90kmh, while yourself driving 130kmh (advised speed) and someone comes up behind you with >170kmh. Changing lanes is much more stressful than eg Belgium which has pretty bad drivers, but they all stick close to the limit of 120kmh, meaning flow of motorway traffic is much more steady.

If the issue really were that drivers don't stick to the limit - enforcement is the answer. Increasing limits does not improve safety on its own.


What exactly is unpleasant in Germany? If you have a guy suddenly behind you then most likely you didn't check properly in the mirror, and estimated speed of approaching car wrongly. You could also perform overtaking manoeuvre more dynamically, just increase the speed when overtaking and reduce after.

Last few months I drive to work on the Germany motorway, and what I can see so far is terrifying. Not fast drivers are the problem but the poor and ashole drivers: - Poor drivers: Me 140/160 km/h, other 120 km/h, and suddenly he/she is changing the lane (to overtake another car ofc), no blinker (you honk at them and they show you the middle finger), nothing! Or switching the lane when when there is not enough space. Jeeez, no! Because you annoyed to drive 117 km/h behind the truck, don't put others in danger. Not everybody in Germany drives 170 km/h or more. So there will be place for you as well, just wait some seconds. Or predict, you see the slow truck in advance, change lane a bit earlier, or show blinker earlier (I always slow down I you give me enough time). Ah, and damn left lane lovers. You overtake them from the right (although you shouldn't) and then they realise "oh shit, I should be in the right one". - Ashole drivers: Driving bumper to bumper even with high speeds, or swaying left to right just to how "hey, I'm behind you" and make a pressure on you.

To summarise, after driving in Germany for 8 years, I love it. I like the discipline although on the motorways is getting worse imho. I'm assuming because of immigration from other countries which don't have good driving habits.

For me unpleasant was driving on motorways in San Francisco area (madness, and not just because of number of lanes), but I was there only for a few days, so maybe my impression is wrong.


What is needed is consistent enforcement. People speed because, most of the time, there are no repercussions. Speed traps feel unfair because they are so rare and arbitrary. A simple solution, blanket our roads with camera speed enforcement everywhere making it consistent and objective. Equip cars with warning lights giving people a chance to slow down before getting the ticket.

"A simple solution, blanket our roads with camera speed enforcement everywhere"

I can't think of any problem with our traffic system that is bad enough to make your solution desirable. Not traffic deaths, arbitrary enforcement, efficiency... nothing.


For me, speeding vehicles and distracted drivers represent the greatest threat to me and my family on a day to day basis. Why not mitigate it? Why it is not desirable to you? What are your concerns?

> Why not mitigate it?

I encourage you to mitigate it. Drive less; that's a great way to mitigate your risk.


Consistent enforcement is an essential element of the rule of law. It's hard to balance against privacy concerns; it's definitely not obvious which is worse: A police force that can fine almost anybody on the road at any time because almost everyone is breaking the law, or a police force that always knows where your car is.

Emotionally, I don't feel as strongly that I have a right to not be tracked when I got out in public as I do that I have a right to equal enforcement. The former seems like a detail of how law enforcement is carried out, the latter seems like a key difference between law and tyranny.


I think the privacy concerns are valid but honestly can be mitigated. I think it is worth trying anyway. If things got out of hand, enough people would complain, and the legislature would reverse it.

In the US governments are only interested in photo enforcement when it's profitable. When laws permit cameras but prevent them from being a revenue source, the cameras go away every time.

Not a word about carrying capacity of junctions, exits, etc... Safety is a secondary concern when it comes to speed limits.

The premise of the article is that the speed limit is uncorrelated with the speed of traffic, other than a small (10%) group of drivers. Therefore reducing the speed limit to eg. Reduce flow into a junction, doesn’t work, people will continue to drive the speed they are comfortable with.

As the article says, people will drive at the speeds that feel safe... in the Netherlands, more and more roads are redesigned for that.

Bumps, parked spots, narrowings and removal of (dividing) lines/road markings are used to bring the traffic back to its intended speed.


Generally when drivers "feel" that a speed limit is too low, it's because the street/road has been over-built. It urban environments, it's inarguable that lower speeds result in fewer fatalities. There's a hockeystick increase in the rate of fatality with pedestrian crashes as vehicle speed increases from ~30mph to ~40mph. See https://nacto.org/docs/usdg/relationship_between_speed_risk_... [PDF]

Speed limits should be set fast enough that nobody should reasonably break them, and then strictly enforced.

In town, 40 mph, if your caught speeding your car is impounded. Highway, speed limit, 120mph. If your speeding, your car is impounded.


I like your basic thought process, but as shown by Germany the correct answer for straight, flat rural highways is to not have a speed limit at all.

120 MPH is pretty reasonable for most interstate-class highways outside of cities though.


Driving on four lane Autobahn can be very stressful, because you have trucks in the right lane going 80 kph (50mph) to save fuel, and the fast guys going 200kph+ (125mph) in the left lane. If you're going some reasonable speed like 130kph, you're endlessly passing the trucks, but you have to watch way back before you pull out for the car or motorcycle going 225. Although it's fun to go fast, I don't think it's a great idea to have more than a 2x difference between minimum and maximum speed on a road.

120 MPH probably exceeds the the speed of reaction time for most drivers. A not-that-tightly packed group of cars going 120 MPH with a single blowout could have devastating effects. There simply isn't enough road to having a following distance big enough. Not to mention there would be entire classes of vehicles not able to safely travel (or travel at all) at such a speed such as semi-trucks.

It is probably on the edge of too fast. That's why it's a speed LIMIT. We've grown accustomed to assuming that the speed limit the speed we should drive at, and going faster is no big deal. I think it contributes to a general disdain for rules. Setting it high enough that there should be no reasonable excuse to break it, should change this.

In a residential area? You come through my neighborhood at 40 and I'll go all Garp on you.

If your neighborhood has roads built for a natural speed of 40 MPH, take it up with whoever built the roads. If you want slow traffic, build slow roads. If you build fast roads, you get fast traffic. No silly sign changes that.

My neighborhood has such a road. It's a road that is a collector road between two highways and a residential road outside of those two highways. However the total width of the road is approximately the same, despite there being more lanes in the collector portion.

I've actually seen cars slow-down when moving from the 25MPH zone to the 45MPH zone due to the greatly reduced shoulder area in the 45MPH zone, but most cars go about 35-40MPH on both sections.


Residential roads should be built so ambulances and fire trucks can go fast. Everybody else should drive slow because they don't want to kill a child.

Ambulances and fire trucks don't need to go fast on residential streets. The difference between fast and slow for those short distances isn't significant even when second count. Of course residential streets should connect to faster highways quickly for that to work.

It's a limit, my point is most people should be going slower then the speed limit and we should let drivers decide up to a point where it becomes unsafe. That's the point where we should enforce with draconian zeal.

Make roads safer, make rules less arbitrary and more respected.


120mph maximum and a 40mph minimum are too disparate.

And there are other deleterious effects of 120mph. > 100 and most consumer tires are at their brink. Similarly, there is a lack of the average vehicle to accelerate quickly beyond 80.


> 120mph maximum and a 40mph minimum are too disparate.

Agreed. The minimum speed for interstate-class highways should be 60 MPH. If you can't do 60, take the country roads.

> And there are other deleterious effects of 120mph. > 100 and most consumer tires are at their brink. Similarly, there is a lack of the average vehicle to accelerate quickly beyond 80.

This is why highways have multiple lanes. Slower traffic to the outside, faster traffic to the inside. If your vehicle isn't capable of keeping up with the fastest traffic, stay to the outside.

Unfortunately Americans in particular are horrible at lane discipline, something I believe is aggravated by speed limits being too low so there's a subset of idiots who take it upon themselves to be speed enforcement and drive slowly in the passing lane.


I don't think it's speed enforcement in most cases. It's usually people not wanting to deal with changing lanes to deal with the slowest traffic.

For a while I would come up across a large number of vehicles inexplicably stacked in the left lane, with a huge gap on the right lane. Younger me would zoom up the gap and inevitably find a semi truck and someone passing it very slowly, and the left lane would close ranks because they thought I was a dick. Older me just stays in the left lane.

edit: I'll move to the right when it's so obviously clear that I won't have to move back to the left. But it's really tedious to be weaving across the road with regularity to maintain a strict adherence to the keep right law.


Oh come on. My 90s shitboxes are all perfectly driveable around 100. Sure they won't get there as fast as a modern car but the only time you find yourself trying to gain 50+mph really quickly is when you happen to be caught on an on-ramp behind someone who has no business driving.

I agree that an 80mph delta is a little much though.


I was just using a couple examples. There's room for other speed limits. I think speed limits should be just that, the max speed you can safely drive at. If someone breaks the speed limit they should have their car impounded.

The current system teaches us that the speed limit is actually a suggested speed, and no big deal to break by 5 or 10 mph. It's a stupid system designed for revenue, not safety.


Absolutely false. Increased speeds have a direct causal link to increased severity of injuries and likelihood of fatalities.

The speed limits aren't too low, the roads are improperly designed for the speed limits that they have.


I love the higher speed limits in northern Michigan (75 for freeways, 65 for highways). There's no reason for a highway to be so slow when there's miles between driveways and intersections.

I can easily believe only 10% of drivers look at the speed limit and drive that speed. But I would have thought that 70% of drivers look at the speed limit and drive some safe margin over -- either +7 mph, or +15 mph. This behavior would be driven by the size of the speeding ticket. Hard for me to believe that none of those people speed up when the speed limit goes up 10 mph.

"Excessive speed" is often cited as a factor in vehicle crashes, but I wonder how much of that factor can be chalked up to speeders trying to spot police instead of keeping their eyes on the road.

It's circular logic. They're basically saying that there exists a low enough speed that could have theoretically prevented this. Whether any reasonable person would have been going that speed is another story. Crashes would be a lot less common if vehicles couldn't travel faster than 20mph. Car crashes would cease to exist if vehicles couldn't move at all.



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