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Angie Schmitt writes in Streetsblog USA that city streets with the widest lanes — 12 feet or wider — are associated with greater crash rates and higher impact speeds and that there is hard evidence that wider lanes increase risk on city streets. Dewan Masud Karim conducted a wide-ranging review of existing research as well as an examination of crash databases in two cities, taking into consideration 190 randomly selected intersections in Tokyo and 70 in Toronto. Looking at the crash databases, Karim found that collision rates escalate as lane widths exceed about 10.5 feet. According to Karim "human behavior is impacted by the street environment, and narrower lanes in urban areas result in less aggressive driving and more ability to slow or stop a vehicle over a short distance to avoid collision. Designers of streets can utilize the “unused space” to provide an enhanced public realm, including cycling facilities and wider sidewalks, or to save money on the asphalt not used by motorists." Karim concluded that there is a sweet spot for lane widths on city streets, between about 10 and 10.5 feet.
According to Jeff Speck the fundamental error that underlies the practice of traffic engineering is an outright refusal to acknowledge that human behavior is impacted by its environment and it applies to safety planning, as traffic engineers, designing for the drunk who's texting at midnight, widen our city streets so that the things that drivers might hit are further away. "When lanes are built too wide, many bad things happen. In a sentence: pedestrians are forced to walk further across streets on which cars are moving too fast and bikes don't fit," writes Speck adding that a pedestrian hit by a car traveling 30 mph at the time of impact is between seven and nine times as likely to be killed as one hit by a car traveling 20 mph This tremendously sharp upward fatality curve means that, at urban motoring speeds, every single mile per hour counts. "Every urban 12-foot lane that is not narrowed to 10 feet represents a form of criminal negligence; every injury and death, perhaps avoidable, not avoided—by choice."
Original Submission
(Score: 0) by Anonymous Coward on Thursday June 04 2015, @03:53AM
This phenomenon -- that drivers go faster when the road feels clearer -- has been discussed here before. [soylentnews.org]
(Score: 2, Informative) by KGIII on Thursday June 04 2015, @11:01AM
This is very much true. Anybody with any sense who models traffic sets inner-city traffic lanes (not "roads" as roads have bicycle lanes, turning lanes, etc.) at ten feet. This slows the traffic to accommodate pedestrians and has the added benefit of increased safety. This does not mean that engineers or municipalities will listen...
"So long and thanks for all the fish."
(Score: 1) by penguinoid on Thursday June 04 2015, @04:07AM
Make lanes as wide as you can but not so wide that people start using it as a double lane?
RIP Slashdot. Killed by greedy bastards.
(Score: 3, Informative) by c0lo on Thursday June 04 2015, @04:20AM
The academia FA [academia.edu], page 6 (?) the "DEVELOPMENT OF SAFETY EVALUATION APPROACH" section reads:
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 2) by c0lo on Thursday June 04 2015, @04:35AM
No, they didn't. Further down, they attempted to take some data points on "line width vs various crash types" for every city and tried a parabolic regression.
Guess what? (see page 6) Sometimes, using only 4 points (side-crashes for Toronto), and... how nice... sometime the fitted parabola shows an (absolute) minimim while closest data point shows a (local) maximum (side crashed in Tokyo). Yeah, and they mixed into some data points from US 1954 - for the context, the earlier seatbelt laws were introduced in Dec 1984 [wikipedia.org] - yeah, no driving culture variability, the data is data is data [venganza.org], right?)
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 2) by gnuman on Thursday June 04 2015, @04:42AM
The last link indicates that there is plenty of evidence from all sources that 10-foot lanes in urban areas are far safer than having 12-foot lanes. Urban areas are not highways.
(Score: 2, Interesting) by Noble713 on Thursday June 04 2015, @05:12AM
Despite higher traffic volumes and population, Tokyo’s crash rates are 34% to 80% lower compared to Toronto’s.
I didn't read the article, but are they also taking into account things like the type of cars on the road? Tokyo's traffic includes a (compared to Toronto) much higher proportion of low-power kei cars (660cc displacement limit, typically about ~65hp). Not to mention a higher age of drivers. A bunch of old people driving glorified golf carts of course aren't going to be involved in as many high-speed collisions.
I wonder why modern megacities aren't developed with the vehicular traffic on the ground level and elevated pedestrian walkways at roughly the second-floor level. Just totally segregate the two types of traffic. The additional expense/maintenance would be worth it, dropping the pedestrian collisions to near-zero and increasing the flow of automotive traffic. Then we could remove a lot of the pedestrian-based automotive design restrictions and give us lower, lighter, sportier automobiles as well.
(Score: 2) by c0lo on Thursday June 04 2015, @05:47AM
Because your implicit assumption* about a "modern megacity" makes it impossible to find one.
*The implicit assumption is that such a "modern" city was developed "modern" from scratch and didn't evolve so from an older one, with its specific constraints and history that worth preserving and no extra (sometimes very high) cost of conversion and with no communities which "oppose such an abomination/eyesore/where are my trees" and whatnot.
A physically equivalent solution: sunk all the traffic in tunnels one level down under utilities - partially adopted by Paris, with its system of 4 ring roads having a significant part of them underground [wikipedia.org] - ain't cheap, that's for sure.
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 1, Interesting) by Anonymous Coward on Thursday June 04 2015, @07:01AM
I would put the cars at least two feet into the ground instead. A car hitting whatever carries your walkways is likely to make them fall down, and cars driving through shop windows and even walls happen all the time.
Hitting a vertical wall of solid ground is going to stop most cars driving at reasonable city speeds.
But then my idea has the problem of how to cross the street, if yours is high enough, people can just cross above the cars.
(Score: 2) by deimtee on Thursday June 04 2015, @12:16PM
Interesting, but you would have the problem of the roads filling with water every time it rained.
If you cough while drinking cheap red wine it really cleans out your sinuses.
(Score: 2) by Immerman on Thursday June 04 2015, @03:01PM
You pretty much have that anyway - it's a rare rainstorm that puddles water deeper than the curb. Hence the network of storm drains to carry away the water. Permeable asphalt would also do much of the job, but that still hasn't really caught on even on normal streets and parking lots.
(Score: 2) by hemocyanin on Thursday June 04 2015, @07:05AM
I live just south of the US/Canada border. We get a lot of traffic from the Vancouver metropolitan area so I don't know if this is a (relatively) rural vs. city driving thing or just a Canadian thing, but Canadian drivers are often very bad: low use of signals, very poor metric to English conversion skills while hogging the left lane, and most of all, very aggressive tactics. There's also the issue with trunk-loads of gasoline -- not a good idea to rearend a random car from Canada on a Saturday.
Anyway, it could be the Vancouver area drivers specifically -- or it could be common throughout Canada ... or it could just be a rural vs. mega-city difference in driving styles that I mentioned before. No matter what it is, I think it would have made much more sense to compare different Canadian cities (or Japanese ones) -- or different roads in the same city. Even in the US, east coast drivers are way more nasty than west coast drivers on average, so comparing some little town in Oregon for example, to a similarly sized town in Massachusetts is not all that valid. Last, so as not to piss off only the Canadians around here, I remember this joke from my time in Vermont: what do you call a Massachusetts driver? Masshole.
Signed,
Mr. Magoo ... (of whom I'm aware solely because of the CBC)
(Score: 0) by Anonymous Coward on Thursday June 04 2015, @07:43AM
And no I-talians. so that has to count for something. A small percentage of Japanese drivers are "baka jidosha". Or following that movie that is up to number six, with dead guys in it.
(Score: -1, Flamebait) by Anonymous Coward on Thursday June 04 2015, @04:28AM
To make whitey avoid hitting their fat black asses. It's passive aggression, pure and simple.
(Score: 0) by Anonymous Coward on Thursday June 04 2015, @04:34AM
(Score: -1, Troll) by Anonymous Coward on Thursday June 04 2015, @04:44AM
Well let's see I was simply making an observation that black people cross the street when they don't have the right of way because they think they deserve to receive preferential treatment for things that dead white people did 150 years ago to dead black people. But sure if you want to reply I guess that makes it a SUCCESSFUL TROLL doesn't it you fucking cockfucker.
(Score: 0) by Anonymous Coward on Thursday June 04 2015, @06:00AM
(Score: 5, Informative) by diaz on Thursday June 04 2015, @04:54AM
This is a basic concept taught in first semester Traffic Engineering at any university: people drive slower when lanes are less than 12 feet wide (the standard width in the U.S.). There are even formulas and tables to calculate how much slower.
(Score: 1) by anubi on Thursday June 04 2015, @06:41AM
Me too. Usually people are parked along the side of the road. When the lanes are narrow, I know there is no room to maneuver should a child, dog, or whatever suddenly appear in front of me and I may be forced to ditch the kinetic energy of my car into a parked car. Either that or hit the kid. Or the thing jutting out of the parked vehicle I cannot avoid by simply swerving around it.
I lived in a neighborhood with narrow streets once, and finding parked cars dented during the night was commonplace. No humans involved, but it was like trying to navigate a theater aisle without stepping on someone's feet.
Once in a while, there is still the a-hole which rips through our neighborhood like it was a freeway. Not all that often though, as the people planning our neighborhood provided no incentive to cut through our neighborhood to get somewhere else. We generally know who the guy is who is, and he gets gently reminded that should he ever have an accident in our neighborhood, he will have a hard time trying to find anyone that won't testify he has a history of ripping through the place.
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]
(Score: 0) by Anonymous Coward on Thursday June 04 2015, @07:08AM
Not new either - I was taught that over forty years ago in Transportation Engineering.
Maybe this stuff is becoming like economics: you get credit (or a Nobel) for proving what everyone already knew.
(Score: -1, Flamebait) by Anonymous Coward on Thursday June 04 2015, @09:56AM
I know they slow down, idiots in the Beemer or Porsche SUVs, cars that are too big for their heads. I hug the centerline between lanes, and they do not even dare to pass, though you can just feel it in their pants that they want to, since they are driving a car that is three times as expensive as mine, but five times as expensive to do repairs on! And they have no depth perception, since they were never required to do any kind of physical work or probably even physics. I love it even more if they honk about their lack of spacial perception, since that will inevitably result in the tightening of clearances. Not a bad as anyone stupid enough honk because they are in a hurry and I am going too slow, since I can always go slower, and often for no more reason than someone behind me alerting me to a possibly dangerous situation for which I ought to slam on my brakes! And if the hit me,, owww, whiplash, and a 2X4 (always a good idea to carry some wood!). So, to sum up, you are not more important than anyone else, the value of your penis compensator grants you no privileges outside of increased liability, and if you drive like an asshole, chances are you are an asshole, and you will not come to, or be, a good end. Get it? Asshole? Good end? Ah, Santorum it!
(Score: 1, Insightful) by Anonymous Coward on Thursday June 04 2015, @05:08AM
Here is another study indicating that either:
1. Lanes are wider in dangerous areas (They might have gotten cause and effect reversed)
2. Danger is correlated with lane width due to come confounding factor (curves? Large Vehicles? higher speed limits? Bad road conditions?)
3. Wider lanes causes danger indirectly, perhaps it increases use of the road, resulting in more throughput, or higher speeds (there might be the goals of having the road in the first place) which then increase the crash rates and crash speeds.
4. Width is dangerous by itself, and don't have benefits.
Really, did they notice that freeways have wider lanes than little city streets and more crashes at higher speeds? There was a similar paper recently about how one way roads were designed to increase traffic flow, but have the nasty effect of increasing accidents. The goal of road design is often more throughput and/or faster traffic. More faster traffic == more accidents. Um, duh. If you make a road 5 feet wide its really safe, but also not useful as a road...
I want to see the same plot broken down by speed limit at least, or a 3d plot of throughput vs lane width vs crash rate. If you want to do real science though try a controlled experiment.
(Score: 1) by dj245 on Thursday June 04 2015, @02:02PM
Here is another study indicating that either:
1. Lanes are wider in dangerous areas (They might have gotten cause and effect reversed)
That's kind of a circular cause and effect though. I would fully expect that wider lanes are employed in newer areas. 50 years ago they weren't building ultrawide lanes in urban areas. So, if the old areas are fine but the new ones aren't as safe, that means something is different between them in regards to the road design. Maybe it's the lane width, maybe it is something else. But the lane width seems the most likely culprit. I've ridden around in Tokyo. People don't get up to very high speeds in any urban area because all the roads are narrow.
(Score: 4, Insightful) by shortscreen on Thursday June 04 2015, @05:54AM
First of all, Mr. Speck needs to get over himself. Criminal negligence? Please. Now, if his idea for improved safety is to have vehicles travel at 20mph instead of 30mph, why doesn't he just say that instead of this baloney about making lanes narrower?
I've heard ideas like this before, but I have a hard time imagining what is going through a person's head. Apparently the root of the problem is that people are having way too much fun driving in shitty urban traffic! Whereas we know that people behave most safely when their task is as frustrating, tedious, and stressful as possible. So we can fix this! Just add more obstacles, more bottlenecks, more confusing signage, more lanes that begin and end and merge and diverge, some spikes that randomly pop out of the road, bottomless pits, death rays that cycle on and off, and... oh! let's make the lanes smaller too!
(Score: 2) by bradley13 on Thursday June 04 2015, @06:55AM
"Whereas we know that people behave most safely when their task is as frustrating, tedious, and stressful as possible. So we can fix this!"
Exactly. Not too far from where I live there is this really terrible intersection: 5 or 6 roads coming in, several crossing tram tracks, a couple of bus lanes, bicycles pedestrian crossings - it's a huge mess, there's nothing to be done because it's a nexus in the middle of a city that has grown up around it. This intersection has a really low accident rate. This, because everyone knows it's bloody dangerous; and everyone is very careful whenever they go through it.
This does not mean that we should make all of our intersections equally dangerous: that's drawing the wrong conclusion.
Where you have need to keep traffic speeds down, fine, make narrower lanes. But make sure that those are not regular commuting routes. Meanwhile, provide commuting routes with wide lanes, away from pedestrians, bicycle lanes, etc..
Everyone is somebody else's weirdo.
(Score: 2) by Phoenix666 on Thursday June 04 2015, @12:57PM
Regular commuting routes should be done on the subway, by express bus, or light rail. If you live in an urban area with sufficient density, commuting by bike trumps even those. Commuting by car is madness.
Engineering roads to be narrower and safer is better for everyone, drivers included. When the road is so wide and design too permissive, risk-taking drivers produce chaotic traffic and accidents that are constantly stressful and dangerous for risk-averse drivers. The result is traffic moves worse through such areas. NYC has started re-engineering its roads along these lines, and as a pedestrian, cyclist, and driver the payoff has been instant for all three modes of travel. The lights have been re-timed so that if you go a constant 23mph you hit all greens in your car, which is beyond wonderful--no more jack-rabbit starts, slaloming between lanes to beat lights, etc. The bikes have their own protected lane, which makes a huge difference if you're a new cyclist. Pedestrians get to not be run down by speeding SUVs.
The only ones who lose are gearheads in their muscle cars, you know, the guys who pull up next to you at stoplights and rev their engines? Personally, it puts a smile on my face if traffic calming frustrates the hell out of those guys.
Washington DC delenda est.
(Score: 2) by c0lo on Thursday June 04 2015, @09:51AM
magic roundabouts [wikipedia.org]
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 3, Insightful) by Katastic on Thursday June 04 2015, @10:35AM
The magic words here: Correlation doesn't equal causation.
Just because narrower roads have less accidentals/slower drivers DOES NOT mean it causes safer roads. You have to control for ALL other factors, but first you must KNOW those factors before you can control for them.
Smaller roads typically also have higher amounts of pedestrians, jay walkers, higher amounts of broken patches of road, and other hazards you have to watch for, as well as higher amounts of sharp turns to avoid large lines of badly parked cars. And those are just off the top of my head.
(Score: 0) by Anonymous Coward on Thursday June 04 2015, @03:08PM
Yes, that actually is what you have to do!
Here's a traffic engineering secret: speed limits are irrelevant. Drivers ignore them and instead go as fast as they feel safe going. No more, no less.
So if you (as an engineer) want to slow down the traffic, you can't do it simply by lowering the speed limit; you have to change the geometry of the road to force the drivers to feel less safe!
(Score: 0) by Anonymous Coward on Thursday June 04 2015, @04:55PM
Replace the airbags with a large spike.
(Score: 2) by darkfeline on Thursday June 04 2015, @07:31PM
Because drivers already obey posted speed limits as it is, right? I love it when I'm driving 5 above the speed limit and everyone else is breezing right past me.
Join the SDF Public Access UNIX System today!
(Score: 1) by Snospar on Thursday June 04 2015, @07:27AM
Yet another dubious statistical analysis linking one bunch of numbers to another bunch of numbers.
I'm pretty sure that on roads with narrower lanes you will still have morons driving recklessly, they won't slow down, they'll just start cutting outside their lane (either into incoming traffic or the new cycle lane).
If you really want to improve road safety start removing the morons from the road. I'm in favour of tougher driving tests and mandatory re-testing every few years. And if you fail your test again and again and again then your license is revoked permanently. Cars are big, dangerous, complicated machines that we hurl around in spaces filled with fragile (dumb) people (including children) - remove the morons and everyone's suddenly a lot safer.
Huge thanks to all the Soylent volunteers without whom this community (and this post) would not be possible.
(Score: 0) by Anonymous Coward on Thursday June 04 2015, @08:22AM
Really? And you're totally confident that you'll pass that ultra-tough test every few years, every single time without fail over and over again and never once be inconvenienced or left without your means of transport? Regardless of each of the examiners' moods or subjective whims? Or do you not actually drive?
(Score: 2) by deimtee on Thursday June 04 2015, @12:14PM
By the time he fails, we should have driverless cars he can ride around in.
If you cough while drinking cheap red wine it really cleans out your sinuses.
(Score: 2) by MichaelDavidCrawford on Thursday June 04 2015, @10:21AM
Real engineering is based on science. Consider that there are materials scientists who will measure the strength of concrete and steel.
Just taking a wild guess doesn't put the "engineering" into "traffic engineering".
I have a close friend who is a well-connected civil engineer; he specializes in highway overpasses. I'm going to pass this article on to him.
Yes I Have No Bananas. [gofundme.com]
(Score: 4, Informative) by quacking duck on Thursday June 04 2015, @04:45PM
I don't know what winter weather is like in Tokyo, but in Toronto and most major Canadian cities we get snow, ice, and other fun stuff during the winter. The wider lanes allow for greater separation between cars and reduce the chances of a minor slippage cascading into a pileup.
It is not uncommon, during moderate snowfall and between times that the snowploughs make another pass, that a 4-lane freeway becomes 3 lanes of traffic spread further apart, as drivers instinctively increase distance on both sides and create tracks on the road free of snow that drivers behind then follow.
(Score: 0) by Anonymous Coward on Thursday June 04 2015, @11:51PM
This isn't about freeways.
(Score: 2) by quacking duck on Friday June 05 2015, @01:45PM
Same principle applies, even more so since in-city roads have no divider between opposing traffic. Hong Kong (article says Tokyo, but I've never been) has noticeably thinner lanes. But Hong Kong doesn't get piles of snow for over a third of every year.
(Score: 2) by Techwolf on Thursday June 04 2015, @07:44PM
Tell that to truck drivers that have to drive those narrow streets.
(Score: 0) by Anonymous Coward on Thursday June 04 2015, @11:55PM
This guy doesn't drive. He either doesn't care how miserable and stressed the drivers are, or he actually likes it.
The extra stress has real negative effects like violence, suicide, and divorce. Commuting is hard on people. We don't need to make it any worse.