They’re the holy grail of transportation engineering: streets and highways specifically designed to encourage automobilists to drive less quickly, reducing the rates of passenger fatalities and generally encouraging a safer urban environment.
And now it appears they just might work: New research from the University of Connecticut suggests that minor reductions in vehicle speed are possible through changes in the street environment. Through the use of roadside parking, tighter building setbacks, and more commercial land uses, road designers can make drivers subconsciously drive more slowly, according to a study of hundreds of roads in Connecticut. It’s a revelatory demonstration of the power of design to change the way people interact with transportation.
For years, the Dutch have been telling us about “self-explaining” roads. According to experiments conducted in the Netherlands, drivers are more likely to follow cues like narrow lanes and street trees than they are to respond to decreases in speed limits. The implementation of these self-explaining streets across that Northern European country has resulted in a significant reduction in automobile collisions, to a point where Dutch drivers are less than half as likely as their American counterparts to die in a road accident. (For a closer look at auto accidents around the world, click here.)
Nevertheless, U.S. transportation engineers have generally ignored this European experience, focusing instead on “forgiving highways” that overcompensate for drivers’ mistakes through generous curve radii and wide lanes.
Unfortunately, while these efforts have been successful in reducing fatalities on the high-speed Interstate system, they’re far less effective for urban situations, where they generally encourage drivers to go faster, putting more drivers, as well as bikers and pedestrians, in danger. Lowering the speed limit has rarely worked to reduce drivers’ speeds, especially for chronic speeders.
Fortunately, a new study of Connecticut roads conducted by University of Connecticut professors John Ivan, Wesley Marshall, Norman Garrick, and Gilbert Hansen, done at the Connecticut Cooperative Transportation Research Program, suggests that the Dutch approach will be effective on U.S. streets and highways. Endorsed by the Transportation Research Board and begun in 2004, the study may change the way we build roads in this country.
The researchers looked at 272 segments of two-lane roads in their home state, choosing to ignore other street widths in order to focus on the specific consequences of differences in design. They collected data for lane width, shoulder width, road width, curves, edge delineation types, sidewalks, building setbacks, density of driveways, and land use. Then they measured the speed of cars “free-flowing” along those respective streets with hand-held radar guns.
The surveys demonstrated that land use type, roadway type, and building setbacks all played significant roles in determining vehicle speeds. Most importantly, though, having cars parked along the side of streets accounted by itself for a reduction in travel speeds of about 2.3 mph, according to a regression study of the research data. Despite this apparently low number, this is a very relevant result because most of the streets had speed limits of 25 to 35 mph — meaning that along residential and commercial streets, parking alone can provide speed reductions of up to 10%.
The study also demonstrated conclusively that, compared to urban and other commercial environments, suburban neighborhoods had higher driving speeds — likely because of fewer distractions for drivers. Similar data showed that the further buildings were set back from the roadways, the faster drivers moved. In other words, the more built-up the environs of a road, the slower drivers went.
So the conclusion is this: People can be induced to reduce their driving speeds when cars are parked along the roadways, when buildings are close to the street, and when those buildings include commercial rather than residential activity.
Granted, this information was already obvious to Dutch road designers, who are proponents of the positive effects of these “self-explaining” roads. Still, we had to find out for ourselves, as it were, and now this American study could influence state transportation departments to change their approach to construction.
Still, will it be enough to dissuade states from continuing to fund suburban arterials that weave through residential neighborhoods and allow drivers to move at high speeds? Only time will tell.
You can find the whole study here.
Image Courtesy of DOT.
March 23rd, 2010 at 1:11 pm
Yonah, great article. You’re right, this is great research. I could not find any links to a report or executive summary. Have they released anything to the public yet? This would be great information to have for presentations.
March 23rd, 2010 at 5:07 pm
An excellent topic. Here is a link to the research, Mr Fredericks.
http://www.trb.org/Main/Blurbs/Designing_Roads_that_Guide_Drivers_to_Choose_Safer_162600.aspx
Eric Dumbaugh has also written about road/urban design and safety. He recently won the Journal of American Planning Best Article 2009:
Eric Dumbaugh and Robert Rae. Safe Urban Form: Revisiting the Relationship Between Community Design and Traffic Safety Volume 75, No. 3
For an earlier article, see: Eric Dumbaugh. Safe Streets, Livable Streets: A Positive Approach to Urban Roadside Design.
It shouldn’t be a massive surprise that people tend to drive faster with more space; however, it seems that current policies do not reflect this attitude. I hope that this report and other research in the area can receive more attention. Decrease speeds and drivers have shorter braking distances. These actions could possibly lead to a decrease in accident rates, resulting in a decrease in emergency response and medical services for a particular troubled road segment.
March 23rd, 2010 at 6:51 pm
Thanks, TAMU student!
March 24th, 2010 at 12:32 am
glad to see what is obvious and understood by many has another good study designed for the US market to back that up!
Speed limit signs do very little, road design truly controls speed, and its time we realized this more fully when looking at designing communities and redesigning cities.
March 24th, 2010 at 3:10 am
[...] Can Roads Control Your Driving? The Truth About Safety-Enhancing … [...]
March 24th, 2010 at 9:06 am
[...] Streets Designed to Slow European Motorists Will Work in U.S. Too (Infrastructurist) [...]
March 24th, 2010 at 11:26 am
Very Interesting! I am a transportation human factors researcher, and I just completed a large research project on similar issues, only from the perspective of individual drivers in simulated driving environments (see http://conservancy.umn.edu/handle/58935).
I found that the proximity of buildings had a direct effect on speed perception/production (i.e., closer led to slower speeds). I also looked at the relative effects of traffic moving at faster/same/slower speeds than the participant drivers and found that this also had a large impact on speed perception/production. Similarly, when both buildings and vehicles were present, drivers were still affected by the visible cues from buildings and had slightly-slower speeds than when just driving with traffic.
March 25th, 2010 at 7:44 am
[...] planning can make streets safer by helping drivers slow down in densely populated areas. The Infrastructurist has a great writeup on the story and they have put a copy of the file online for [...]
March 26th, 2010 at 1:12 pm
[...] Streets Designed to Slow European Motorists Will Work in U.S. Too (Infrastructurist) [...]
March 30th, 2010 at 1:03 am
[...] Can Roads Control Your Driving? The Truth About Safety-Enhancing … [...]
March 30th, 2010 at 11:25 am
Yay - just what we need. Roads designed to make traffic move even slower than it already does!!
March 30th, 2010 at 11:40 am
[...] the holy grail of transportation engineering: streets and highways specifically designed to encourage automobilists to drive less quickly, reducing the rates of passenger fatalities and generally encouraging a safer urban environment. [...]
March 30th, 2010 at 11:50 am
Unfortunately, a number of the factors which make roadways *seem* less safe to drivers, thus causing them to drive more slowly, may actually make the roads less safe.
Putting parked cars (and the passengers who exit them) and buildings (and the children who live in them and play around them) closer to the roadway will likely lead to increased risk for those bystanders.
Now narrow lanes and tree-lined roadways sound like a good way to induce drivers to be more careful without putting pedestrians in harm’s way.
March 30th, 2010 at 11:52 am
This study is retarded and idiotic.
Who would have thought that by reducing a driver’s visibility, the driver would go slower to give themselves time to react to surprises? You? You in the back? Are you some kind of smartass? The Connecticut Department of Transportation studied this for four years [trb.org]. There’s no way you could have arrived at the same conclusion so quickly!
This study was useful in determining how much people slowed down — quantifying it at about 10% — but sweeping on to claims like, “reducing the rates of passenger fatalities and generally encouraging a safer urban environment” is silly. Streets packed with parked cars, pedestrians, nearby buildings, et. al. are generally more dangerous precisely because clear lines-of-sight are cut off. Sane drivers know this, reduce their speed, and then — making wild hand-waving guesses, here — wind up with about the same overall level of “dangerousness” as when driving on uncluttered roadways.
March 30th, 2010 at 11:56 am
I can’t believe I am reading this! You want to make the streets more narrow, place obsticles on the street, and obstruct vision, to slow people down? Those things can easily be read as, “We want to make the roads more dangerous, so there is a higher probability of accidents, but at lower speeds. This therefore makes the roads safer!” So you are trading frequency for strength of events. Sounds like you are just shifing the balance, and not solving anything. What kind of moron would think this to be a good idea?!
We all call it traffic “Flow”. Yes, there are different forces on each “particle” (vehicle), and some seemingly random behavior, but traffic can be modeled somewhat with modeled fluid dynamics. Its pretty obvious high accident locations are high turbulence areas. You are reccomdening increasing turbulence! Your theory slower more chaotic flow is safer than laminer flow (less chaotic, higer speed). Like I said before, you are trading one for another. You aren’t solving anything. Design the roads properly, for laminar flow, provide safe ways for pedestrians to cross, keep signals highly visible, keep the intersections highly visable, and keep the freaking pedestrians following the laws set forth, and that will “solve” your problem. Its been stated over and over and over again. Check with the National Motorist Association for studies, test cases, etc. Not many intend to run lights, or crash, or hit pedestrians, more often than not, its poor design. Traffic Cameras, tougher enforcement, and your new “idea” of slowing things down by making it more dangerous, are just ludicrous and don’t work. You’re shooting the fire extinguiser at the flames, rather than the fuel. Just engage that frontal lobe and use some logic. The only problem you’ll find is “It’s too expensive to fix the right way”, well, how many lives has it cost not to fix it? Should have designed it right in the first place. Take your punishment, fix it, and learn your lesson, don’t design roads improperly in the future. (This article is actually reccomending building roads wrong)
Its sad that this is what so called experts come up with….
March 30th, 2010 at 12:11 pm
I planned to say what Kirby Files said, that these factors, parked cars etc., induce lower speeds because they are a hazard making lower speeds appropriate. Trees lining the roadway are also a hazard, so the same reasoning applies.
The solution is coming. All cars will be software controlled in a few years. Just stay alive and in one piece until then.
~ Nehmo
March 30th, 2010 at 12:19 pm
Slowing down is great, but why cause more congestion?
March 30th, 2010 at 12:38 pm
As a pedestrian who was hit by a driver unable to see around all the cars parked on the side of the street (I was in a marked crosswalk, with flashing yellow lights, giant yellow signs and yellow paint on the ground with 3 of 4 lanes having cars stopped to let me cross), I can tell you this is a WONDERFUL idea. Yes, let’s make cars slow down to be safe and not worry about the pedestrians they are now unable to see.
It’s also a good idea to make the cars drive in narrower lanes, closer to the parked cars making it nearly impossible to open the door of that parked car… oh, and let’s make all the heavily congested side streets even slower: all that stop and go driving is good for the environment.
March 30th, 2010 at 12:53 pm
Tom Vanderbilt’s book “Traffic: Why We Drive the Way We Do (and What It Says About Us)” discusses this in particular as well as many other ways human psychology affects driving. Recommended.
March 30th, 2010 at 1:02 pm
“Someone” should visit Cambridge MA and drive down Columbia St. They have done all of the classic “traffic calming” techniques that he lambastes. And yet accidents are way down and the street is much safer. It “feels” and “looks” unsafe and drivers slow way down! Amazing how that works! Now it is safe for bicycles because they can keep up with the cars.
Give people “laminar flow” and they will pretend they are on the freeway. As a counter example, look at Walnut St. in Somerville MA. It was supposed to be turned into a freeway in the 60’s and people treat it as such today. Zoom zoom zoom. As a result there are many many accidents on this street (my wife’s car was destroyed while parked on it) and it is unsafe for bicycles. Urban streets are not meant for travel, they are meant as access to the dwellings within neighborhoods. If you wanna go fast, get on the fast highway.
“Should have designed it right in the first place.” What an unbelievably ignorant comment. Perhaps you are unaware that automobiles are 100 years old and our older cities are pushing 400 years old. Compared to our cities, automobiles are a passing fad.
Hey you can pontificate all you want from your suburban sprawl house, but those of us who live in the actual city know that these techniques work well.
Yes I studied Urban Planning at MIT.
March 30th, 2010 at 1:21 pm
It is beyond me that someone would actually design to decrease traffic flow. Are you dense? Traffic will be.
They did my downtown like that and now I can’t back out of a parking spot without almost getting creamed.
March 30th, 2010 at 1:23 pm
I just spent a week in Cambridge and my biggest complaint and unbelievable frustration was it took 45 minutes to go 5 miles. I actually stopped leaving the hotel it was so bad.
Thanks for validating my claim that this reduces traffic flow.
March 30th, 2010 at 1:42 pm
“They did my downtown like that and now I can’t back out of a parking spot without almost getting creamed.”
That’s only true if people are NOT slowing down. Driving in a calmed road is frustratingly slow, but it is safe, because you see these thigns coming, and tap the brake.
March 30th, 2010 at 1:51 pm
”
I can’t believe I am reading this! You want to make the streets more narrow, place obsticles on the street, and obstruct vision, to slow people down? Those things can easily be read as, “We want to make the roads more dangerous, so there is a higher probability of accidents, but at lower speeds. This therefore makes the roads safer!” So you are trading frequency for strength of events. Sounds like you are just shifing the balance, and not solving anything. What kind of moron would think this to be a good idea?! ”
It makes it a little more likely that you’ll ding your car.
It make it a LOT less likely you’ll kill anyone.
March 30th, 2010 at 2:17 pm
The Dutch die less in accidents because they drive less. Less people own vehicles, more public transportation is available, the country is smaller and getting around is easier. I am sure their driver education is better as well. Compare apples to oranges much?
March 30th, 2010 at 2:40 pm
New Yorkers also drive less. Less people own vehicles, more public transportation is available, the city is smaller and getting around is easier.
Yet they die far more often in car crashes, because the streets in New York are designed for higher speed.
March 30th, 2010 at 3:22 pm
@Von Datch: You’re trying to say that the researchers decided to compare basic figures between Netherlands, population 16.5 million, and the US, population 309 million? I doubt even a stupid researcher would do that.
I suspect, rather, that they compared relative figures, like percentage of car owners involved in accidents, deaths per 1000 drivers, etc. Go on, prove me wrong.
March 30th, 2010 at 5:19 pm
“Someone” should visit Cambridge MA and drive down Columbia St. They have done all of the classic “traffic calming” techniques that he lambastes. And yet accidents are way down and the street is much safer. It “feels” and “looks” unsafe and drivers slow way down! Amazing how that works! Now it is safe for bicycles because they can keep up with the cars.
If you want bicycles to keep up with the cars, remove the cars from the road. If the goal is to make things “slow” enough, and therefore “safe enough” for bycicles, but don’t want to remove the cars, take the finanancial pain, and cut paths for bicycles. I do realize how old these towns are, just how painful this would be, and that cars are new to them. However, if in the 1940s they decided that these vehicles are getting faster and more dangerous, they could have started projects to make it safer, the right way, for pedestrians, bicycles, and motorists. The longer you wait, the more painful the financial burdon. Honestly, though, the way you talk, it sounds like you are in fact, in favor of banning cars, and having the most technologically advanced, fastest vehicle allowed being a segway. Cars were an improvement over bicycles, and horses. They wern’t meant to be air conditioned boxes that don’t require a living source of energy, but other than that be the same thing as a horse and buggy. You however, seem to be implying this, and no, I won’t agree with that one bit.
Also, let me clarify, I was not advocating “traffic calming”, that is also ludicrous. Instead, make the intersections so that you CAN SEE pedestrians in the cross walks. Make it so when you are in the left turn lane, you can see enough oncoming traffic to determine if it is safe to turn. Make it so as you are coming over the hill, you already know the light is red before you get there. If you give people the information they need to be able to not accidently strike a pedestrian or bicycle, they won’t. That is what I suggest, and indeed many non-profits back me up on that.
Of course, everything I’m saying is based on the pedestrian or bicyclist is obeying the law (lights, DON’T WALK signs, etc). If they break the law, all bets are off.
Now, I know you are going to take this personally, but honestly, it has to be said, and I don’t mean it personally. I looked at the spring course offerings at MIT’s Urban Planning and Development catelog. I did not see a single math class, logic class, physics class, or anything else science/engineering oriented. So, I am guessing, albeit, and educated guess, this is not a science degree, nor an engineering degree, and therefore has no real structure to build itself on, other than what some people think has worked in the past. In other words there are no axioms, theroms, lemmas, or any other small fundamental provable premises for which anything this coursework offers. Only history, and narrow interpretations thereof. That’s not what I want controlling my life. I want strict, provable, repeatable, logic, and no statistics do NOT count as proof. So would I ever take the word of an “Urban Planner”? No, not ever, not more than a lawyer, or a politician. This reminds me of so many other “fields” which claim to conduct studies, and claim to be scientific, which I personally classify as pseudo-science, lacking the rigor and proof that real science requires. Like I said, don’t take it personally, its directed at the field as a whole. I am sure that if it included math modeling and simulation, they could come up with some very fundamental rules of traffic, and given, time, money, and access to modify intersections to control all but 1 indedpendant variable, could experimentally prove these fundamental theorms. Perhaps that is just too optimistic though.
March 30th, 2010 at 5:42 pm
If you want bicycles to keep up with the cars, remove the cars from the road. If the goal is to make things “slow” enough, and therefore “safe enough” for bycicles, but don’t want to remove the cars, take the finanancial pain, and cut paths for bicycles.
There is no need for bikes to keep up. The only need is for cars to travel slow enough that accidents involving cars have a low severity. And under 25MPH, that’s how it works. Cars might get dented or even totaled, but injuries are mild.
Also, let me clarify, I was not advocating “traffic calming”, that is also ludicrous. Instead, make the intersections so that you CAN SEE pedestrians in the cross walks. Make it so when you are in the left turn lane, you can see enough oncoming traffic to determine if it is safe to turn.
Nice theory. The data do not bear it out. In most of the US, you can see far ahead when you make a left. And yet, left turn accidents are commonplace. In places that have put in traffic calming, you don’t see that far ahead, so you have to be cautious. And accidents are less frequent and less severe.
Now, I know you are going to take this personally, but honestly, it has to be said, and I don’t mean it personally. I looked at the spring course offerings at MIT’s Urban Planning and Development catelog. I did not see a single math class, logic class, physics class, or anything else science/engineering oriented
Nobody at MIT who studies at the department of Urban planning studies ONLY at that department. Everyone takes courses at the other departments. Don’t take it personally, but you need to stop making uninformed assumptions like that.
March 30th, 2010 at 6:42 pm
Ok now really, you need to listen to yourself. So first off you seem to think 25 MPH is a rule of thumb. Ask any motorcyclist who has had an accident at 25 MPH not wearing a helmet what he thought of his “minor injuries”, oh wait, you probably can’t, he’s probably dead. Being accellerated to 25 MPH in a fraction of a second, by a small section of your body is trauma enough, then stopping suddenly, especially via the head is tragic, if by the skin, it’s still pretty damaging. Why don’t you pull up some pictures of survivors of people struck by cars moving 25 MPH. Survivability isn’t the only factor to look for, quality of life is another, so I don’t want to hear another word about speed, and fatalities. Its clearly a simple expression of the preservation of life instinct, without any engagement of the logical thought center.
The data does in fact bear out the theory, you simply choose to ignore it and substitite your own snobbish conclusions, since after all, you went to MIT, and clearly don’t have a lot of practical world experience. Caution means danger, danger is bad. I hope thats simple enoughfor you and your idiodic friends to understand, the second you start saying bad=good, is the second you have stepped out of the logical and into the illogical, and therefore irrational.
Funny how you say you study other things, but don’t list a single one. Could it be your sense of morality is telling you not to lie, but you don’t want to show you aren’t involved in any sort of scientific, or engineering field? It could be you don’t want to brag, but so far you haven’t shown that inhibition, so I’m going to call that doubtful. Further, anyone who continually cites college, as I previously stated, has probably little to 0 real world experience. Just wait till you get into industry, you’ll see how much you really know! Having graduated from a school with an excellent national reputation (PennState, maybe not as good a name as MIT, but still nothing to sneeze at either!) myself, I had the same pride…until some guy from some no name school showed me some pretty cool (by cool I mean mathematical/scientific stuff) that was part of the companiy’s research, and which I knew nothing about. Thats when you realize your school has little to do with anything except getting you a job, and provide networking later. I still love PSU, and I still root for their football team like crazy, but it was just college….a very short period in your life, or at least it should be…
March 30th, 2010 at 6:53 pm
Sounds like communism to me…
March 31st, 2010 at 1:27 pm
Ok now really, you need to listen to yourself. So first off you seem to think 25 MPH is a rule of thumb.
A rule of thumb that is backed by study after study, including the ones posted here.
Ask any motorcyclist who has had an accident at 25 MPH not wearing a helmet what he thought of his “minor injuries”, oh wait, you probably can’t, he’s probably dead.
And irrelevant.
Being accellerated to 25 MPH in a fraction of a second, by a small section of your body is trauma enough, then stopping suddenly, especially via the head is tragic, if by the skin, it’s still pretty damaging.
Except, when the prevailing speed is 25MPH, you don’t get accelerated to 25MPH. At 25MPH, drivers have shorter braking distances and better reaction times. So if you’re hit, you’re hit at far less speed. And, at 25MPH, cars are easier to dodge, so you’re less likely to be hit, period. Which is why traffic calming saves lives.
The data does in fact bear out the theory, you simply choose to ignore it and substitite your own snobbish conclusions, since after all, you went to MIT,
You went snobby on Fran by assuming she has no education in physics. You got fed a dose of your own medicine. That’s life. You presume to know about traffic safety, when traffic safety depends on human action as much as it depends on physics. Which is why Fran can lecture you on it and perhaps you should let her.
April 5th, 2010 at 10:52 am
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