Tag Archives: #SciAmCities

The Science Of Driving And Traffic – the importance of breaking the rules

I wrote this post back in December of 2006 (yes, I think my writing has improved since then) and not much has changed except that the roundabout on Hillsborough Street in Raleigh has been in place for a while now, I drove it several times, and it seems to be fine (though they had to add signs ahead of it to teach the drivers how to use a roundabout) and is certainly successful in eliminating congestion.


Let me state up front that this is not a topic I know anything about, but I have always had a curiosity for it, so let me just throw some thoughts out into the Internets and see if commenters or other bloggers can enlighten me or point me to the most informative sources on the topic. This is really a smorgasbord of seemingly disparate topics that I always felt had more in common with each other than just the fact that they have something or other to do with traffic. I am trying to put those things together and I hope you can help me.

1. Models of Traffic Flow

There are two kinds of people modelling traffic: traffic engineers and physicists. The former use traditional modelling techniques, while the latter indulge themselves in using more esoteric methods, e.g., cellular automata, etc. The traffic engineers, apparently, are not too fond of the models developed by physicists, and I always wondered what the reason for this was and tended to dismiss it as mere professional jealousy and turf-protection. But now I think there is a deeper reason – the two groups do their modelling with two different motivations.

The physicists are testing the math and playing with the computers. Their models are applicable not just to traffic but also to other types of flow, e.g., blood flow. Their main goal is to figure out the conditions that determine when the flow will be smooth, when there will be stop-and-go traffic, and when the whole thing will be ground to a stop.

The traffic engineers, on the other hand, have two goals: smooth traffic flow is one of them, but the other one is to ensure the maximal safety of every individual participant in traffic, something that physics models are barely starting to address. The engineers’ goals are practical – how to build roads in a way that maximizes flow AND maximizes safety. For that, their models have to incorporate not just the behavior of the entire system, but also the behaviors of each individual driver based on the real-life behavior of people operating motor vehicles (as well as cyclists and pedestrians). The physics models have only recently made some baby steps into incorporating realistic human behavior into their models. After all, humans beings behave differently in traffic than red blood cells in blood circulation.

I could not find a study that I remember from a few years back that shows that the “jerks”, those people we hate because they speed and weave in-and-out of lanes, actually contribute to smooth flow – without them, the traffic would be more likely to get congested. Although the speeders only shave off a couple of minutes of their own traveling time, their behavior prevents the blockage of traffic and thus also shortens the travelling time for everyone else.

For (I think) excellent summaries of the current state of traffic modelling I recommend these two articles: Stop-and-Go Science and The Computer Minds the Commuter. Is there anything better or more recent I should read?

2. City Traffic

Most of the traffic flow models I read about deal with the flow and congestion on highways. I could not find that much on modelling traffic of city streets. Such models must exist, though, as someone must have made some calculations when suggesting roundabouts on Hillsborough Street in Raleigh (the street that serves as a northern border of the North Carolina State University campus). For the heated debate about this, check out this excellent blog post and comments and this commentary, just to quickly get up to speed. This discussion has been going on for quite some time now, with quite strong feelings exhibited by the two sides of the issue – the pro and con groups. I have nothing empirical to base my feelings on, but I instinctively aligned myself with the pro-roundabout side. It just felt right. Am I wrong? Why or why not?

3. Car Safety

About a year ago, I have read (in ‘Discover’ magazine, I believe), several people’s essays on the “Future of the Car”. Most wrote about new gizmos and gadgets, more entertainment, and more automation. But one was thinking completely out of the box and I loved it! How to improve safety of the cars, he asked? Not by building bigger, harder and stronger cars with more and more nifty safety features – that is just a never-ending arms-race. Instead, take a lesson from the inflatable gas bags – what makes it useful is its softness, not hardness! So, the author argues, why not make the OUTSIDE of the car as soft as a marshmallow? People would still not want to bump into each other because it affects their own speed and direction, but if such a contact occurs, nobody gets hurt! Brilliant!

4. Geography of Driving Philosophy

I learned to drive back in Belgrade when I was about 18 (min. driving age there), but never bought a car so I did not drive there very much. Still, the driver ed there is a long grueling process, about 40 lessons stretching over several months. During the course, I drove on the highway and in miniscule city streets. I climbed a mountain (and drove back down again on a very narrow twisty road). I drove out in the woods outside the city in freshly fallen deep snow (and my instructor and I helped a couple of other people get their cars out of the ditches). When the city streets were covered with ice one day, my instructor made me go to the hilliest part of town and taught me how to negotiate very steep uphills and downhills on ice.

But, although the driving school was just a couple of blocks away, I had to wait until almost the end of the course until I was allowed (Allowed? Forced – I was terrified!) to try to negotiate Slavija (see picture) – a huge roundabout in the very center of Belgrade where there are absolutely no traffic signs! There are some simple basic rules of traffic applicable to the situation, but most of the rules were actually unwritten rules and all the traffic around it was based on driver-driver negotiation. The way people drive there, everywhere in the country but nowhere felt as palpably as on Slavija, is by such driver-driver negotiations: one part applied psychology, one part hand-and-eye signals.

When I arrived in the United States I had to start driving because there is no other way to get from A to B. And that is when I realized that the driving philosophy is different here – it is not based on negotiations, but rather on strict obedience to much better defined nitty-gritty rules. There are exceptions – driving in Manhattan is more Europen-style in this matter and there may be some other geographical differences within the USA. See this and this for examples.

There is something about this that makes me uneasy. I have a feeling that many people here drive on ‘automatic pilot’, lulled into complacence by a naive expectation that strict following of rules will automatically make them safe. I see it in myself. When I have a sense of flow and a full awareness of my surroundings I drive much safer but that also means that I often buck the rules. After all, the rules are just suggestions, the scaffolding on which we build our driving behavior using our knowledge and experience.

When we drive we make decisions every moment. Most of the time, the decisions we make will be within the rules and laws of traffic. But sometimes, the best decision is to not follow the rules. Safety is the primary concern. When it is satisfied, efficiency comes in as a second concern, followed by wish to minimize wear-and-tear of the car, greater comfort for the driver and passengers, and the fuel efficiency. Blind obedience to rules often does not satisfy either one of these, and when safety is challenged, bucking the rule is the best thing to do.

But, I got a couple of tickets the other year for “rolling through a stop sign” so now I obediently stop. And I discovered that this gives me a false sense of security – I do not pay as much attention to what is really happening in traffic around me. That is unsafe!

What I think is happening is that these stop signs are unnecessary – they should not be there – and when I drive well, somewhere deep inside my mind there is a decision to ignore the sign because it is an obstruction in the way of safe driving. They are inside Southern Village – a little urban village that looks like a toy-set for kids. The fact that the streets are paved at all is kinda nice, and that streets have names is probably useful for the mailman, but traffic signs are totally useless and counterproductive because everyone here drives within the “negotiation paradigm” of driving. Unfortunately, there is a police station in the Village and some cops find it easy to hide in the narrow curvy streets (especially the corner or Parkside and Meeting streets) and quickly gather a bunch of tickets from me and my neighbors without having to go too far [Note; I have moved out about a year ago]. And who is going to argue cognitive science and the physics models of traffic flow with a guy who so clearly enjoys the power of his badge and his gun (and his BLACK uniform – I thought that no police or military force in the world, after the WWII, would be so stupid to use black uniforms of the SS again – as a son of a Holocaust survivor, my first visceral reaction to a black uniform is distrust and fear, not something that makes the cop’s job easier to do)?

So, I was really happy to find that I am not the only one who thinks that most traffic signs are unnecessary or even potentially dangerous. Garry Peterson wrote a great post about this very topic, in which, among else, he quotes from this excellent Wired article:

Hans Monderman is a traffic engineer who hates traffic signs. Oh, he can put up with the well-placed speed limit placard or a dangerous curve warning on a major highway, but Monderman considers most signs to be not only annoying but downright dangerous. To him, they are an admission of failure, a sign – literally – that a road designer somewhere hasn’t done his job. “The trouble with traffic engineers is that when there’s a problem with a road, they always try to add something,” Monderman says. “To my mind, it’s much better to remove things.”

Riding in his green Saab, we glide into Drachten, a 17th-century village that has grown into a bustling town of more than 40,000. We pass by the performing arts center, and suddenly, there it is: the Intersection. It’s the confluence of two busy two-lane roads that handle 20,000 cars a day, plus thousands of bicyclists and pedestrians. Several years ago, Monderman ripped out all the traditional instruments used by traffic engineers to influence driver behavior – traffic lights, road markings, and some pedestrian crossings – and in their place created a roundabout, or traffic circle. The circle is remarkable for what it doesn’t contain: signs or signals telling drivers how fast to go, who has the right-of-way, or how to behave. There are no lane markers or curbs separating street and sidewalk, so it’s unclear exactly where the car zone ends and the pedestrian zone begins. To an approaching driver, the intersection is utterly ambiguous – and that’s the point.

Monderman and I stand in silence by the side of the road a few minutes, watching the stream of motorists, cyclists, and pedestrians make their way through the circle, a giant concrete mixing bowl of transport. Somehow it all works. The drivers slow to gauge the intentions of crossing bicyclists and walkers. Negotiations over right-of-way are made through fleeting eye contact. Remarkably, traffic moves smoothly around the circle with hardly a brake screeching, horn honking, or obscene gesture. “I love it!” Monderman says at last. “Pedestrians and cyclists used to avoid this place, but now, as you see, the cars look out for the cyclists, the cyclists look out for the pedestrians, and everyone looks out for each other. You can’t expect traffic signs and street markings to encourage that sort of behavior. You have to build it into the design of the road.”

Definitely read Distracting Miss Daisy, On “Distracting Miss Daisy” and WHERE THE SIDEWALK ENDS for more thoughts about the idea that too much regulation, and too many signs, are actually making us less safe in traffic:

Books: ‘On The Grid’ by Scott Huler

Every September, the Scientific American magazine tackles a broad topic. This year, the theme is Cities. This is only the third time the magazine has tackled this topic (it was also done once in 1920s and again in 1960s). The magazine articles will be rolled-out on the website over the next month, and our staff has prepared a number of additional Web-only features. It is not surprising that our network bloggers are going to chime in with their own blog posts about the topic (a few have already been posted this morning). I intend to write one or two myself, but to get us started, I will re-post, from the archives of my old blog, a post or two first. Let me start with my review of “On The Grid”. While the author, Scott Huler, is a good personal friend, as well as a blogger at Plugged In blog on our network, I can say that my overwhelmingly positive review is real: I really liked the book (and would have not reviewed it, for a friend or not, if I did not like it). I first published this review on July 5, 2010.


About a month ago, I told you about the book-reading event where Scott Huler (blog, Twitter, SIT interview) read from his latest book On The Grid (amazon.com). I read the book immediately after, but never wrote a review of my own. My event review already contained some of my thoughts about the topic, but I feel I need to say more, if nothing else in order to use this blog to alert more people about it and to tell everyone “Read This Book”.
infrastructure 001.JPGWhat I wrote last month,

“I think of myself as a reasonably curious and informed person, and I have visited at least a couple of infrastructure plants, but almost every anecdote and every little tidbit of information were new to me. Scott’s point – that we don’t know almost anything about infrastructure – was thus proven to me.”

infrastructure 003.JPG…was reinforced when I read the book itself: I don’t know anything about infrastructure. But after reading the book I can say I know a little bit, understand how much I don’t know, and realize how much more I’d like to know. I bet it was fun watching me as I was reading it, exclaiming on average five times per page “This is so cool”, and “Hey, this is neat” and “Wow, I had no idea!” and (rarely) “w00t! Here’s a tidbit I actually heard of before” and “Hey, I know where this is!” (as I lived in Raleigh for eleven years, I know the area well).
infrastructure 006.JPG

A few years ago, Scott was just as ignorant about infrastructure as most of us are. But then his curiosity got better of him and he started researching. He would start at his house in Raleigh and trace all the wires and cables and pipes going in and out of the house to see where they led. Sometimes there would be a crew on his street digging into the asphalt and fixing something and he would approach them and ask questions. At other times he would figure out where the headquarters are and who to ask to talk to:
infrastructure 007.JPG

“What Scott realized during the two years of research for the book is that people in charge of infrastructure know what they are doing. When something doesn’t work well, or the system is not as up-to-date as it could be, it is not due to incompetence or ignorance, but because there is a lack of two essential ingredients: money and political will. These two factors, in turn, become available to the engineers to build and upgrade the systems, only if people are persuaded to act. And people are persuaded to act in two ways: if it becomes too costly, or if it becomes too painful to continue with the old way of doing things. It is also easier to build brand new systems for new services than it is to replace old systems that work ‘well enough’ with more more modern ways of providing the same service.”

infrastructure 008.JPGIn a sense, this book is a memoir of curiosity as Scott describes his own adventures with a hard-hat, a modern Jean Valjean sloshing his way through the Raleigh sewers, test-driving the public transportation, and passing multiple security checks in order to enter the nearby nuclear plant.
infrastructure 009.JPGBut it is more than just a story of personal awe at modern engineering. Scott weaves in the explanations of the engineering and the underlying science, explains the history and the politics of the Raleigh infrastructure, the historical evolution of technologies underlying modern infrastructure, and illustrates it by comparisons to other infrastructures: how does New York City does that, how did Philadelphia did it 50 years ago, how did London 500 years ago, how about Rome 2000 years ago?

“What is really astonishing is how well the systems work, even in USA which has fallen way behind the rest of the developed world. We are taking it for granted that the systems always work, that water and electricity and phone and sewers and garbage collection and public transportation always work. We get angry on those rare occasions when a system temporarily fails. We are, for the most part, unprepared and untrained to provide some of the services ourselves in times of outages, or to continue with normal life and work when a service fails. And we are certainly not teaching our kids the necessary skills – I can chop up wood and start a wood stove, I can use an oil heater, I know how to slaughter and render a pig, how to get water out of a well, dig a ditch, and many other skills I learned as a child (and working around horses) – yet I am not teaching any of that to my own kids. They see it as irrelevant to the modern world and they have a point – chance they will ever need to employ such skills is negligible.”

infrastructure 015.JPGAnd this brings me to the point where I start musing about stuff that the book leaves out. As I was reading, I was constantly hungry for more. I wanted more comparisons with other cities and countries and how they solved particular problems. I wanted more history. I wanted more science. I wanted more about political angles. But then, when I finished, I realized that a book I was hungry for would be a 10-tome encyclopedic monograph and a complete flop. It is good that Scott has self-control and self-discipline as a writer to know exactly what to include and what to leave out. He provides an excellent Bibliography at the end for everyone who is interested in pursuing a particular interest further. His book’s homepage is a repository for some really cool links – just click on the infrastructure you are interested in (note that “Communications” is under construction, as it is in the real world – it is undergoing a revolution as we speak so it is hard to collect a list of ‘definitive’ resources – those are yet to be written):
OnTheGrid homepage.jpg
infrastructure 022.JPGWhat many readers will likely notice as they go through the book is that there is very little about the environmental impacts of various technologies used to ensure that cities function and citizens have all their needs met. And I think this was a good strategy. If Scott included this information, many readers and critics would focus entirely on the environmental bits (already available in so many other books, articles and blogs) and completely miss what the book is all about – the ingenuity needed to keep billions of people living in some kind of semblance of normal life and the interconnectedness that infrastructure imposes on the society, even on those who would want not to be interconnected:
infrastructure 027.JPG

“There are people who advocate for moving “off the grid” and living a self-sufficient existence. But, as Scott discovered, they are fooling themselves. Both the process of moving off the grid and the subsequent life off the grid are still heavily dependent on the grid, on various infrastructure systems that make such a move and such a life possible, at least in the developed world.”

infrastructure 031.JPGMy guess is, if there’s anyone out there who could possibly not like this book, it will be die-hard libertarians who fantasize about being self-sufficient in this over-populated, inter-connected world.
infrastructure 032.JPG

At several places in the book, Scott tries to define what infrastructure is. It is a network that provides a service to everyone. It has some kind of control center, a collection center or distribution center. It has a number of peripheral stations and nodes. And there are some kinds of channels that connect the central place to the outside stations and those stations to the final users – every household in town. There is also a lot of redundancy built into the system, e.g., if a water main breaks somewhere, you will still get your water but it will come to you via other pipes in surrounding streets, with zero interruption to your service.
infrastructure 025.JPG

Scott covers surveying of land, stormwater, freshwater, wastewater, roads, power, solid waste, communications (phone, broadcast media, internet) and transportation (e.g., public transportation, trains, airplanes). These are the kinds of things that are traditionally thought of as ‘infrastructure’. But aren’t there other such systems? I’d think security has the same center-spokes model of organization as well: police stations and sub-stations (distribution centers) that can send cops out wherever needed (distribution channels), with potential criminals brought to court (processing centers) and if found guilty placed in prison (collection center). Similarly with fire-departments. Ambulances are just the most peripheral tentacles of the health-care infrastructure. The local-county-state-federal political system is also a kind of infrastructure. So is the military. So is the postal system. So is the food industry and distribution.
infrastructure 018.JPG

Thinking about all of these other potential examples of infrastructure made me realize how many services that require complex infrastructure undergo cycles of centralization and decentralization. For transportation, everyone needed to have a horse. Later, it was centralized into ship, railroad, bus and airline infrastructures. But that was counteracted by the popularity of individually owned cars. And of course taxis were there all along. And as each decade and each country has its own slight moves towards or away from centralization, in the end a balance is struck in which both modes operate.
infrastructure 020.JPG

You raised your own chickens. Then you bought them from mega-farms. Now many, but not most citizens, are raising their own chickens again. It is not feasible – not enough square miles on the planet – for everyone to raise chickens any more. But having everyone fed factory chicken is not palatable to many, either. Thus, a new, uneasy balance.
infrastructure 011.JPG

Nowhere is this seen more obviously today as in Communications infrastructure. We are in the middle of a big decentralization movement, away from broadcast (radio, TV and yes, newspaper industry infrastructure with its printing presses, distribution centers and trucks) infrastructure that marked about half of 20th century, and forward into something more resembling the media ecosystem of the most of human history – everyone is both a sender and a receiver, except that instead of writing letters or assembling at a pub every evening, we can do this online. But internet is itself an infrastructure – a series of tubes network of cables and it is essential not to allow any centralized corporation to have any power over what passes through those cables and who gets to send and receive stuff this way.
infrastructure 013.JPG

Finally, as I was reading the book I was often wishing to see photographs of places or drawings of the engineering systems he describes. As good as Scott is at putting it in words, there were times when I really wanted to actually see how something looks like. And there were times when what I really wanted was something even more interactive, perhaps an online visualization of an infrastructure system that allows me to change parameters (e.g., amount of rainfall per minute) and see how that effects some output (e.g., rate of clearing water off the streets, or speed at which it is rushing through the pipes, or how it affects the water level of the receiving river). That kind of stuff would make this really come to life to me.
infrastructure 030.JPGPerhaps “On The Grid” will have an iPad edition in the future in which the text of the book is just a beginning of the journey – links to other sources (e,g., solutions around the globe, historical sources), to images, videos, interactive visualizations and, why not, real games. After all, it is right here in Raleigh that IBM is designing a game that allows one to plan and build modern infrastructure – CityOne. These two should talk to each other and make something magnificent like that.


The small images are thumbnails – click on each to see the whole picture, full-size.