Traffic Calming

June 17, 2005 6:09 PM

Slow 'em down. "Traffic calming is the combination of mainly physical measures that reduce the negative effects of motor vehicle use, alter driver behavior and improve conditions for non-motorized street users." If you are a frequent pedestrian user of a residential street with high traffic volumes, or speeds, you may be interested in strategies and data from various community projects to alter traffic flow.
posted by paulsc (40 comments total)

well some of the traffic calming strategies arent very sophisticated.. textured sidewalks and some what raised side walks, as well as speed bumps.. i have seen them all.. I think these minor impediments to drivers have little "traffic calming" effect. a little bump in the road or some textured sidewalk wont stop people for driving at high speeds. it will slow them down for a moment, but they'll be sure to pick up the speed soon afterwards. Besides, some roads have natural bumps due to the fact that repaired cracks are paved over unevenly, creating a rather bumpy surface. And even on these drivers manage to speed..
posted by gregb1007 at 6:28 PM on June 17, 2005

Ironically, fire trucks are motor vehicles. If you're considering getting speed bumps installed in your street, ask your local fire department to explain the effect on response times and damage to fire trucks.
posted by aeschenkarnos at 6:31 PM on June 17, 2005

That's great. Let's make driving even less efficient.
posted by Kwantsar at 6:32 PM on June 17, 2005

Yeah, none of that shit calms me down at all when I am driving; to the contrary, it kinda pisses me off. What they should do is configure roads in such a way that I don't have to drive through random residential areas to get where I am going.
posted by donkeymon at 6:39 PM on June 17, 2005

What they should do is configure roads in such a way that I don't have to drive through random residential areas to get where I am going.

So you want to completely alter the entire built-environment of a city to meet your demands of getting from point A to point B 5 minutes faster?

Pedestrians are also found (or should be found) in commercial areas as well, not just "random residential areas", so where DO you want to put our roads?
posted by Boydrop at 7:43 PM on June 17, 2005

Though its focus isn't on residential areas, I'm reminded of this Salon article (if one doesn't have a subscription, one can hit this link to skip the ad).

"A new school of traffic design says we should get rid of stop signs and red lights and let cars, bikes and people mingle together. It sounds insane, but it works."

More directly relevant is the NMA's anti traffic calming info.
posted by vira at 8:16 PM on June 17, 2005

Cool, I disagree with everyone up to Boydrop! I bet you are all under the age of 25.

Let's see ... who knows better about whether traffic calming devices actually work: traffic engineers who have studied these problems for decades, or keyboard potatoes who had thought about it for 15 seconds?

I'm not a traffic engineer, but I am an engineer in another discipline, and one of the things that I've learned is that other engineers aren't stupid. They know exactly what they're doing, especially the older ones. The only time that you see badly engineered systems is when the engineering talent has been pulled off due to budget or competing demands, or there weren't real engineers involved in the first place.

The traffic calming devices in my neighborhood do indeed have precisely that effect on me. I soon as I hit that section of road (the core retail district, teeny tiny, just a couple hundred feet) I do feel the urge to back off the accelerator, even when there's no traffic. And I do normally drive with a lead foot, I drive a high-performance car, blah blah blah.

aeschenkarnos's comment does recall one problem we've noted in our neighborhood though: the narrower streets do present problems for turning emergency vehicles, buses and delivery trucks.

on preview: vira is also exempted my generational snark at the top
posted by intermod at 8:20 PM on June 17, 2005

sky bridges built on command directly from point to point? I don't know but I agree with donkeymon.

They put a "Traffic circle" in an intersection near my house, basically all they did was place a large un-driveoverable circle of concrete in the center of the intersection, and replace the two way stop with a four way yield.

This is extremely stupid, because the visibility coming onto the "main" road from the dead end road I live on is terrible. You have to pull up to approximately 1 yard from the stupid concrete circle to see if anybody is coming, at which point they will of course hit you.

While you might have a point about roads never being totally convenient, people do often seem to make these nonsensically double-ended subdivisions, which encourage through traffic that ALWAYS travels 40+ mph.

If they want low traffic, don't open up both ends. Everything else is a temporary impediment, followed by an opportunity to have some fun with the accelerator. Or I suppose you could get some police cruisers out there to actually enforce the laughable 25 limits on those roads, but I doubt residents really want that, as they'd be the ones being pulled over, and of course the entire desire to make people drive 25 is hypocritical nonsense that people seem to cave to in order to make roads "safe for children". (As soon as those people are actually driving on the roads, they want the limit at 50 like everybody else).

(When the stupid concrete circle went up some people protested it by going and getting a deer carcass and draping it over the bushes and stuff in the center of the circle. Sometimes living in Alabama is funny.)
posted by SomeOneElse at 8:40 PM on June 17, 2005

Chicanes and chokers are actually very effective for the typical sane drivers. But in any urban American environment with the average number of idiots on the road they do not have much effect. I am continuously amazed at the flagrant and suicidal risks people take to make it to the next red light five seconds faster than the next guy. The only real hope is a future with automatically controlled vehicles which require no input from drivers. The Intelligent Transportation System (ITS) holds much more promise in traffic calming than these methods. Technologically it is feasible but it will require an industry wide effort to outfit cars with the required guidance systems. With the ideal ITS system, there will be very little driver input. Infrastructure changes would actually be minimal.
posted by JJ86 at 8:49 PM on June 17, 2005

My favorite form of defacto traffic calming exists in Georgetown (D.C.) where the road is made of large cobblestones and there are old trolley tracks in the middle. You can't drive more than 15/20 mph.
posted by shoepal at 8:51 PM on June 17, 2005

Heh, yeah cobblestones or big potholes work well in taming traffic......
posted by JJ86 at 8:52 PM on June 17, 2005

Seriously, they can't be THAT suicidal because there are still plenty of those people around.

Automatic controls = wussy.
Ok, that's too mean but honestly I do not look forward to that, it's creepy to call it the only hope for the future. The present itself is not even that hopeless.
posted by SomeOneElse at 8:56 PM on June 17, 2005

Chicanes and chokers and bulb outs and speed bumps and speed humps et. al are all really just bandaids for poorly written code/zoning.

For anyone that is interested (in sprawl, etc.), DPZ's SmartCode [pdf] is an interesting read.
posted by shoepal at 8:58 PM on June 17, 2005

I live in a residential development, 2 blocks off a 6 lane divided main avenue, in a mid-sized city in the Southeastern U.S. At rush hours, when traffic is moving in and out of this subdivision, frustration is palpable at the intersections out on the boulevard, which are controlled by stop lights. People accelerate and corner madly, to "beat" the light cycles, and, in the 6 months I've lived here, there have been an average of 2 injury wrecks a week at the nearest corner intersection, which also abuts a chain coffee restaurant that is popular with the drive up window morning commuter crowd.

Driver psychology is clearly in play, as outside of rush hours, the incidence of squealing tires, revving engines, and honking horns is noticeably less. But unfortunately, for 4 hours a day (2 hours in the morning, 2 in the evening) most days, being a pedestrian around here is dangerous at every street crossing in the neighborhood, as frustrated drivers from the big avenue try to "make up time" on narrow residential streets.

And even though I drive these same streets, I have to admit, if it wasn't for the daily bit of walking my dog, and walking to nearby shops and restaurants on weekends, and seeing a lot of the carnage in some of those wrecks, I don't know that I would think much about this area while driving through it. In that way, intermod and I share the same personal reaction to some of the changes being requested for my neighborhood, beyond a couple of entrance islands that have already been installed. Going around the islands, I now have a reminder to "watch it" in this area, as I "decompress" from 55 mph avenue traffic, into this neighborhood.

The phrase "traffic calming" seemed pretty apt when I heard it a few weeks ago, in a request to sign a petition being passed around the neighborhood. And frankly, I was happy to sign, because of what I'd seen myself in the past few months around here.

I think some of the points regarding emergency vehicle issues raised in materials in the NMA site that vira linked may be cause for pause when considering traffic calming devices, but I think some of this is highly route specific, too. And I guess I'd reply to SomeOneElse's points by saying that a traffic calming device shouldn't be, itself, a traffic hazard, obviously.
posted by paulsc at 9:31 PM on June 17, 2005

My dad is a paramedic, and he really really hates all these traffic calming measures.
He's on the ALS (advanced life support; mainly for heartattacks) crew and the minutes added by the traffic calming can make the difference between the person being resuscitated A-OK or having the person suffer permanent brain damage/death.
posted by Iax at 10:15 PM on June 17, 2005

Atlanta for some strange reason decided to go with traffic humps rather than bumps. These are bumps that have been stretched to four feet to minimize the 'bump' effect.

IOW, they are absolutely useless for slowing anything with more than 4" of ground clearance, which by my reckoning is most everything out there short of mopeds.
posted by mischief at 10:30 PM on June 17, 2005

Someoneelse said that "of course the entire desire to make people drive 25 is hypocritical nonsense that people seem to cave to in order to make roads "safe for children". (As soon as those people are actually driving on the roads, they want the limit at 50 like everybody else)."

Safe for the children isnt the only reason to reduce the speed limit: you also want to make it safe for adults to cross from one side of the road to another while talking a walk through the neighborhood... Whether people stroll, jog, or run like a professional athletes, no one wants to struck by a 50mile per hour car while they are it
posted by gregb1007 at 1:56 AM on June 18, 2005

Traffic calming is part of a system, not the one and only solution to fixing a system.

A city that wants to be good for business and residents needs traffic calming in areas where people will not drive safely without a cop sitting on the corner. It also needs residential streets with barriers that open only for emergency vehicles and local residents, though the gates should be designed so an emergency vehicle could crash through if the gate didn't work. It needs city businesses to encourage employees to use public transportation. It needs a good public transportation system paid for by parking charges -- park your car outside the congested area for a price but then use your parking stub to ride public transport all day for no additional charge. It needs to put police officers on public transportation -- no city police officers should be driving to or from work except in an emergency (but keep them in uniform and on the clock for travel time). And a big city needs congestion charges like the system that is working well in central London.

Such measures in combination can make a city more pleasant and safe to live and shop in, and that's great (financially and otherwise) for a city.
posted by pracowity at 6:16 AM on June 18, 2005

shoepal wrote:

Chicanes and chokers and bulb outs and speed bumps and speed humps et. al are all really just bandaids for poorly written code/zoning.


I'm not sure where you draw that conclusion. Code/zoning has nothing to do with people driving fast. Most areas have posted speed limits which are ignored by idiots. Zoning is strictly the location of residential and commercial areas of a city.
posted by JJ86 at 6:19 AM on June 18, 2005

I, for one, have found traffic calming to be a botch when the underlying problem is the inadvertant creation of a rat-running arterial due to bad planning, lousy traffic controls and generally stupid city traffic engineers.

The most hilarious local traffic calming fiasco is the main arterial running due north to our only hospital. The city put traffic circles in the intersections. Now I can run that street at 75 mph on my motorcycle while the cars just doodle along.

The real solution is to block one end of the street at the arterial to keep the residential areas out of the traffic flow and prevent them being used as shortcuts.

But the most entertaining solution is to install Phalanx guns set to obliterate anything not an emergency vehicle moving at more than 5 mph over the speed limit. Think of it as evolution in action.

I, of course, would install a hacked IFF on my vehicles and challenge the out of town college students to street racing, thereby solving two problems at once.
posted by warbaby at 6:30 AM on June 18, 2005

The choker implementations I've seen are pretty annoying for bicyclists. But I think that's more of a bug than an inherent flaw--space could be made between the choker and the curb. On the other hand, the humps are almost fun on bikes.
posted by A dead Quaker at 6:34 AM on June 18, 2005

They should make everyone drive a motorcycle one month a year. That would make people more aware of thier surroundings get them in the habit of LOOKING AROUND. Nothing keeps you on your toes like riding around on a bike with a bunch of people that are constantly trying to kill you.
posted by password at 6:56 AM on June 18, 2005

If what you want is calm drivers, just legalize marijuana and require everybody to drive stoned. You might get a few people sitting through several cycles of traffic lights before remembering sheepishly that they were supposed to go when the light turned green, but you'd get a lot less agressive driving, and road rage would become a thing of the past.
posted by alumshubby at 7:28 AM on June 18, 2005

The most effective measure I've seen being used to slow down traffic over here are unmanned camera's. They are popping up everywhere, some crossings having eight or more of them.
Five years ago, you where considered slow if you were only driving 10km/h above the speed limit. Now, you will find most people driving 10km/h below the speed limit which themselves have already been lowered from 90 to 70 in many places. So on roads were a few years ago, the average speed was 100km/h, it's now 60km/h.

Another effective measure I've seen being used is the narrowing of roads. The narrower the road, the slower one drives. The streets around my home are two two way streets, but by allowing people to park on both sides of the roads, there is not enough space for two cars to cross each other. It seems to work without causing traffic jams.

Also new are traffic lights that automatically jump to red if you approach them faster then the speed limit allows.
posted by Timeless at 9:04 AM on June 18, 2005

A few years ago in Chicago there was a big boom in cul-de-sacs on residential streets. The sidewalk continues but there are concrete barriers so traffic can't cut through.

There are a few areas where I live (western suburbs) where they added these ginormous speed bumps. Really uncomfortable to go over them no matter what speed you're driving.

Also new are traffic lights that automatically jump to red if you approach them faster then the speed limit allows.


Wow, that would suck.
posted by SisterHavana at 9:42 AM on June 18, 2005

As someone who bikes in traffic every day, I can say authoritatively that people in cars need to chill the fuck out. I live next to an interstate on-ramp, and people use the approaches to accelerate up to, easily, 40 mph.

All those who are wondering about emergency response time, I would have them consider the number of people who are injured in traffic accidents. And more importantly, the various insanities caused by modified exhaust systems.

People need to realize that driving around in a car is not the only perspective in life, there is riding a bike, people walk, and most importantly -there are people who live in these areas that function as urban drag strips.

Granted, a large part of the problem is people who don't give a shit. I guess that will never change-not until people are willing to be birthed from their metal wombs and realize that there is a whole world *outside* their cars.

I encourage everyone to drive 5 mph under the speed limit, it's refreshing how it can change your perspective.
posted by kuatto at 9:42 AM on June 18, 2005

Speed humps are great on a dual-sport motorcycle, that much I can tell you. :-)
posted by five fresh fish at 10:20 AM on June 18, 2005

Post a 25 m.p.h. speed limit; stick a speeding camera somewhere; et voila. People will learn.
posted by carter at 10:35 AM on June 18, 2005

Let's see ... who knows better about whether traffic calming devices actually work: traffic engineers who have studied these problems for decades, or keyboard potatoes who had thought about it for 15 seconds?

Of course, one forgets that traffic engineers that studied traffic for decades built the roads that suck in the first place.

Engineers built tacoma narrows bridge, too.

And so we hand the problem over to engineers again? No. You Fail It.

*MOST* traffic calming is stupid. Fix the road design instead (as in block off streets as others have said, AND BUILD NEW ONES where they were SUPPOSED TO BE).

If you install enough traffic calming you will NOT get people to ride the bus/use a bike/walk to work/[insert greenie pipe dream here]. You will, instead, cause people to move away and help destroy the city's economy. You know what happens to roads in a city that's broke? You can be assured the money won't go into more traffic calming, that's for damn sure.
posted by shepd at 10:38 AM on June 18, 2005

More cameras, that's what we need. Enforce the speed limit, raise revenue, don't hinder emergency vehicles.

As a bike commuter I'm 100% with kuato on this one. I'm fed up with nearly getting killed just so somone in a car can get to the next set of lights marginally faster than the bloke in the next vehicle.
posted by handee at 11:08 AM on June 18, 2005

Not to derail, but...

I guess one of the things I'd hoped to discuss in this thread, that some of you have touched on, goes back to the post phrase "traffic calming." If we can accept that traffic is an important social activity, that has a large component of individual decision making and responsibility, and that such responsibilities are, on the public ways, best excercised by calm but involved drivers, shouldn't we be looking for ways to promote and reinforce the appropriate mental states in individual drivers? If so, what's the best way of doing that, and how can road design aid in doing it?

alumshubby suggests (facietiously, I hope!) that we require all drivers to be stoned. gregb1007, warbaby, A dead Quaker and others raise the non-auto perspective, and seem to confirm what I've noticed, that people in cars that are tense, angry, or really late don't easily shift mental states in response to changes in locale, unless presented with some stimulus to do so. The traffic calming mechanisms of bumps, chicanes, narrowings and such may be effective, but aren't the whole answer, and come with drawbacks of their own.

So I guess what I'm asking now is "If bumps and such aren't the way to get drivers 'traffic calm,' what works for you, and how do we extend that in more urban to neighborhood transitions?"

As an example, I've noticed that an older town about 5 miles from here has a lot of tree-lined streets, and there seems to be a lot better voluntary compliance with the prevailing 25 mph speed limit there. The same urban boulevard runs right into that town's center, and makes a right turn at a stop light into a similar 4 lane state highway. But there are rarely any crashes at intersections there, and few times that I remember hearing any squealing tires, or seeing anybody "jumping" lights. It's as if the tree lined side streets magically soak up aggression!

Problem is, it takes 50 years to grow those kinds of trees...
posted by paulsc at 11:12 AM on June 18, 2005

One more thing:

Since statistically, it's mostly men that drive too fast, I suggest that strategically placed brothels with girls behind windows is a sure way to slow down traffic.

This is true of the Chaussée d'Amour, a road famous for its brothels in this area. Most cars slow down or are forced to slow down so that the drivers can get a better view of the girls waving back at them from behind their windows. The police have in fact gone as far as pulling over drivers for driving too slow.
I was actually surprised that they had placed unmanned camera's here as well. I would think that the chance of catching anyone speeding here would be very slim. (but that is assuming the camera's are actually pointing towards the road and not some place else).
posted by Timeless at 11:14 AM on June 18, 2005

One of the best effects of traffic calming is to increase drivers yielding behavior. Drivers are more likely to yield to bikes and peds when they are driving at 25mph instead of 35 to 40mph in residential zones.

The other tidbit to consider is that when a car hits a pedestrian at 20mph there is a 5% chance of killing them. At 30mph the chance that a pedestrian is killed rises to 45%. At 40mph the chance that a pedestrian is killed by a car rises to 80%. The faster you drive the greater the threat you are to pedestrians.

From the 1950's to 1990's roads were only designed for cars.
Engineers did not design roads for bikes or pedestrians. That is beginning to change. The Institute for Traffic Engineers has design guides on what traffic calming works and the effect that it has on accident rates.

http://www.ite.org/traffic/index.html

Also see Walkable Communities
Walkability is the cornerstone and key to an urban area's efficient ground transportation. Every trip begins and ends with walking. Walking remains the cheapest form of transport for all people, and the construction of a walkable community provides the most affordable transportation system any community can plan, design, construct and maintain. Walkable communities put urban environments back on a scale for sustainability of resources (both natural and economic) and lead to more social interaction, physical fitness and diminished crime and other social problems. Walkable communities are more liveable communities and lead to whole, happy, healthy lives for the people who live in them.

http://www.walkable.org/

Perils for Pedestrians is a monthly television series promoting awareness of issues affecting the safety of people who walk.

http://www.pedestrians.org/index.html

America Walks is a resource for folks who advocate for sidewalks and walkable communities.

http://www.americawalks.org/
posted by meddeviceengineer at 1:09 PM on June 18, 2005

I would prefer to see more walkable communities. I'd also prefer to see people moving to areas where they can walk or bike to work rather than having to drive; these areas are already becoming popular in the city I live in.

Traffic calming does work. There are ways to do it where it really will have a great effect; traffic is just a system and flow through systems is very well understood. Unfortunately, most of the implementations are poor. The reason that most implementations are poor is because a neighbourhood will sit on a city councillor to "Do SOMETHING!" and they will do "SOMETHING" ... it just won't be effective.
Part of my job is to design computer interfaces. Part of the art of desinging good interfaces is that you subtlely guide the user through the system by providing almost subliminal hints using color, texture, and sight-lines. The same principles could extend to roads if the <sneer>engineers</sneer> would stop beleiving they're gods of system design and take some external advice.

I personally like traffic circles. They force people to slow down, and require the usually brain-dead drivers to think. After replacing a 6-entrance uncontrolled angled intersection a year ago with a nice, large traffic circle, accidents dropped from one a week down to none, and speed limits dropped in the area. They've got a great track record in europe.

I hate speed humps, bumps, whatever. On the other hand, I have a car with a very nice suspension, and I like accelerating enough to catch air off the far side. So yeah, put more in. (If that didn't clue you in to the effectiveness of traffic humps, it should.) Add the loathing that emergency workers of all stripes have for them, and it's a wonder they keep getting installed. (Insert another snide comment about Mrs. Grundy of the Neighbourhood Association here.)

The problem with traffic cameras is that the constitutionality is far too easy to question. One of the main tenents of our judicial system is that you get to face your accusor. When your accusor is a camera, it's a little hard for the prosecution to do.
On top of that, here in Oregon, people started vandalizing and destroying the cameras. There's only so many times that the city is willing to replace an acid-etched camera surface before they're just going to turn off the camera, and that's what's happened.

I still think traffic calming is a good solution, but I also think the problem is larger than just the traffic. We can't forget that it's a system and that change in one part will have unintended consequences elsewhere, and also that basic psychology teaches us that people who are boxed in and channeled like cattle react unpredictably.
posted by SpecialK at 3:58 PM on June 18, 2005

I prefer traffic calming measures that involve high-powered lasers.
posted by five fresh fish at 5:26 PM on June 18, 2005

The only time that you see badly engineered systems is when the engineering talent has been pulled off due to budget or competing demands, or there weren't real engineers involved in the first place.

Definetely arguable. But even if it's true there are a lot of things that have been brilliantly engineered to do something completely stupid.

Traffic calming works pretty well in London, and the total chaos/fear method works pretty well in Amsterdam too in my personal experience. But there is one thing I think we're all forgetting and that thing is: Snow. I cannot even imagine what would happen if they had to plow the streets of London with all the bollards, chicanes, small roundabouts etc. they have in place but I think it would be pretty damn tricky.
posted by fshgrl at 7:33 PM on June 18, 2005

Have you guys seen speed limit signs, that flash the speed you are driving at? I think those are pretty effective -- at least on me.

Also, I wouldn't mind hidden cameras, if you were given some free passes. The meter maids at my grad school give me free passes sometimes by just leaving warnings on the car. Even when they leave a ticket, I don't get as irritated as I used to, and actually feel a little guilty. I don't know if they just do this randomly, based on the day, or the time or what. In undergrad, I used to get a ticket every time (never a warning). Let's just say, my undergrad institution has already received its alumni contribution.
posted by nads at 12:46 AM on June 19, 2005

I like the speed limit signs that flash the speed you should be driving at, if you wish to make the next light as an uninterrupted green.
posted by five fresh fish at 7:36 AM on June 19, 2005

JJ86 wrote "Code/zoning has nothing to do with people driving fast."

I beg to differ. Wider streets (as often found in suburban hoods) actually inadvertently encourage drivers to go faster than they should. Narrow streets, particularly with on-street parking discourage speeding. Street widths are coded/zoned.

So, in fact, coding/zoning have a lot to do with the speeds on a given road.
posted by shoepal at 10:45 PM on June 19, 2005

As another bike commuter, I support any measure than will cause motorists to calm the fuck down. Jesus Christ. Getting behind the wheel seems to turn normally relaxed people into competitive confrontational asses. This is a road, where people are conveying themselves to various destinations, not the Daytona Speedway. No one said you'd be able drive at the maximum possible speed all the time.

The main argument I hear against traffic calming measures is the increased response time for emergency vehicles. I suspect that many of these emergency vehicles are responding to preventable motor vehicle collisions.

Also new are traffic lights that automatically jump to red if you approach them faster then the speed limit allows.
Ok, this is awesome. This is one of the coolest measures I have heard about. They should make all lights like this. I can't believe I haven't heard of this before.
posted by recursive at 1:06 PM on June 20, 2005