An Einsteinian thought experiment about transport

Let’s remember how useful it can be to ask new questions, remembering how Albert Einstein asked himself questions that led to his discovery of the special and general theories of relativity.[1]
Are there not many questions we need to be asking about how to organise our transport — our systems and modes of transport? Our current system — globally — is massively destructive, killing millions every year, [2, 3] maiming tens of millions, [2, 3] and is a leading cause of catastrophic global warming. [4] That is just the start of the list: it also destroys space and natural life, kills tens of millions of animals every year, [5] pollutes air, water and land, requires gigantic money costs, etc. We ought to change our transport system. How?
Well, how can we think about transport? For example, what goals do we want to solve with transport? Simply put: where do we want transport to take us? Maybe there is an interesting physical relation to consider, and this brings us to a kind of Einsteinian thought experiment.
An Einsteinian thought experiment. Imagine, for example, a transport, like a jet-pack, that enables people to move in all directions at infinite speed. Then no one can move or even stand safely anywhere! One person on a jet pack — moving at infinite speed in any direction, prevents any other person from being safe wherever they may be.
That is to say, some people travelling fast and freely (e.g. by car) means that others are limited, in their ability to move or even stand anywhere! The Einsteinian thought-experiment leads to the idea that: One body moving more means other bodies must move less. I.e. when one body moves extremely fast in a range of directions, other bodies must limit their freedom of movement (speed / direction). There is a safety limit in terms of vector/speed.
This form or equation of the physical relation can describe the problems of cars, that combine (with roads) many vectors and high speed, and therefore, limit the speed/vector for other persons or bodies.
Let me try to apply this general relation to ordinary examples: A child playing in the street, is at danger when other objects/persons travel in that space at injurious speeds. The child’s range of movement (speed and vector), e.g. just bouncing a ball around, or painting on the pavement, is limited by these other moving bodies, to the extent that the child simply cannot play in the street safely. This is amazing: even extremely modest/limited movement by a child in the street is obviated (made impossible) by much more expansive (high speed/large vector range) movement by other objects. We see this historically in our societies, as children’s freedoms of movement have become extremely limited, by the spread of the car, for example, but really it is any high-speed/high-vector moving object (even a bicycle, I’m sad to have to say).
Gravity is an invisible force; and maybe what we’re working with in understanding the physical relationships of transport is also invisible, to some extent.
– The effective sphere for the imaginary jet pack I described is gigantic; as a result, the effective sphere for all other bodies (that are vulnerable to that jet-pack) shrinks to near-zero, or even zero (there is no safe place at all!).
– The effective sphere for a car-user is large — the car-user can move at high speeds along many vectors. As a result, the effective sphere for bodies that are vulnerable to the car, shrinks.
How can we use this physical relation understanding?
Movement is relative! One fast moving body means that other bodies must move slower or not at all — if they share space!
Vectors are important! If bodies don’t move in the same space (i.e. along the same vectors), then the relation is not so large. A mundane example: segregating bicycle traffic from pedestrians enables higher speed for bicyclists, and more speed/vector range for pedestrians.
We need to consider all movement in our world: it’s not just human beings who need to move around! Animals, birds, i.e. non-human life also needs to move around. And non-animate nature needs to move around too: water, for example, as considering the hydrological cycle confirms. Consider a situation where a human transport system destroyed the hydrological cycle (the movement/cycling of water through various stages and phases): it wouldn’t last long!
Walking is amazing! Perhaps the relational idea about movement helps us understand yet again (from a new standpoint) why walking is so amazingly good, and beneficial! Well, at the slower speeds of walking, one can preserve more vectors of movement. Walking down a city street, one can do a million things (and one preserves others’ freedoms also). Driving fast down that street, one cannot do much; and one limits others too. A city street only for walking (as transport) enables millions of activities — is “convivial”, lively, etc. A city street designed for moving at high speed, disables.
At a global level, we can see that new questions arise: what forms of movement (human, non-human, non-animate), are important, necessary, sacred?
Car-free is better:
(1) Given a certain amount of space, like a town of 10 km diameter, the freedom of movement is far greater without the car than with the car. The space is usable in more ways.
(2) When distances expand, and people wish to accomplish those distances rapidly, then the range of transport vectors should be limited. High-speed rail is an example of an extremely limited vector range (only the track), and so it can travel at high speeds, over large distances, without much impact on other people’s freedoms of movement. (Japan’s elevated high-speed rail tracks take it to another level!)
(3) In a sense, the car is our world’s real version of the imaginary jet-pack that I described above. It’s a technology for a person to “enjoy” transport at high speeds on a wide range of vectors. The results are there for everybody to see: the range (or freedom) of movement for others shrinks.
Cars have other wasteful/destructive qualities: among them, they have a very low density of passengers, relative to other forms of transport, like walking, cycling, buses and trains. One could have a car-free city of 50 km diameter, with high-speed motorised transport (bus, train), and be fairly safe, if the motorised transport forms were extremely segregated from other bodies.
[1] A nice summary of these processes of asking interesting questions by Albert Einstein is provided by the book from White and Gribbin, Albert Einstein, A life in science. (preview available here)
[2]  WHO (World Health Organization), Global status report on road safety, 2009,
[3] WHO (World Health Organization), The global burden of disease: 2004 update,
[4] “In 2004, transport was responsible for 23% of world energy-related GHG emissions with about three quarters coming from road vehicles. Over the past decade, transport’s GHG emissions have increased at a faster rate than any other energy using sector (high agreement, much evidence).” a quote from p. 325, of IPCC, 2007, “Transport and its infrastructure”, chapter 5 of the Fourth Assessment Report, Climate Change 2007: Mitigation of Climate Change.
[5] One million animals killed every week globally was the figure cited in Natural Capitalism, the 1994 book by Paul Hawken, Amory Lovins and L. Hunter Lovins. The book is available free here:

This article was originally published on the blog of Aaron Thomas:
thank you for allowing us to publish this interesting post.

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End of the Road: Tranno Letter

I’ve read articles, letters to the editor and now a front page story on an issue that some claim to be a top priority; potholes. But the most important element in the debate is not discussed. Transportation is all about friction and weight. People are not taking personal responsibility for the problem.

The problems with street surfaces have grown in proportion with the growing size and number of our vehicles. Families used to share one car and drive fewer miles in vehicles that weighed 2700 pounds. Now 70% of vehicles sold locally are trucks and SUV’s.  SUV’s average over 4500 pounds. The wear and tear of our roads is directly related to the weight of our vehicles.

A practical and appropriate method to address paying for our streets would be for DMV to sort their database and assess fee’s based on the curb weight of each registered owners vehicles. People who walk, bike and ride mass transit would not be required to pay for pothole repair.

Perhaps a “curb weight tax” will hasten the movement away from the large vehicles, which make roads unsafe for small, clean and efficient vehicles. Roads that support only lightweight vehicles need significantly fewer repairs.

But wait. Any spending on roads today is folly. We’ve exhausted the fuels and fouled our environment with a system based on internal combustion and diesel powered, room-sized, tank-like vehicles. Instead, utilize those assessments, fees and tax dollars in the design and construction of the infrastructure for our transportation future.

To the Editor, Eugene Register-Guard, March 3, 2008

J.L. McKinney

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Carfree Days: A Glimpse of the Future


Dhaka by Debra Efroymson

While sitting in a van with colleagues from the more lucrative part of my job (the part that doesn’t involve urban planning or transport), stuck in typical Dhaka traffic one day, a man who to my knowledge has never worked on urban issues explained to a visiting American how wonderful the city is when there are hartals, or political strikes. “It’s great,” he gushed, “there are almost no cars. It takes far less time to get around by (cycle) rickshaw than it does on other days by car. Other than the tear gas and violence, it’s perfect.”

He could have added that the streets are quieter, and if the hartal lasts two or three days, the air becomes surprisingly clean and fresh, despite a population of about 12 million people. He could have added how sociable the city becomes, with groups of children cycling down the middle of the streets, and groups of adults walking together to work or to a shop.

In some ways hartals are not a fair example of what the city could be like carfree. After all, many offices and shops stay closed, so there are far fewer people moving about. And of course the violence, and the suffering of those who live day-to-day and who cannot earn money during hartals adds a grim aspect. On the other hand, how many other opportunities does one have to experience one’s city car-lite or carfree? And if rickshaws can be faster than cars, why are they attacked as slow-moving transport while cars are not just allowed but encouraged?

When moving about Dhaka, I can’t help but notice how small the city seems when traveling by rickshaw or bicycle as opposed to car. Sitting in a car stuck in traffic, the city seems huge and unfriendly, destinations widely spaced, and no form of transport viable except the car. But when there is a hartal, or early in the morning when traffic is light, the city magically shrinks in size; faraway destinations become readily accessible without the use of an engine. This is only partly because the trip can be faster when non-motorized. Realisation slowly dawns on me: if traveling were pleasurable it wouldn’t matter if it did sometimes require more time, as one could then mix leisure and recreation with transport, rather than travel being solely for the sake of arriving somewhere else.

But if I mentioned to the colleague who waxed rhapsodic about hartals that one could achieve a similar, but more peaceful, effect by getting rid of the cars, he would react with disbelief. On a hartal, sure, rickshaws are great, but for day-to-day life cars are essential, despite only a tiny minority of the population having access to them. Cars are inevitable, as much so or more than political unrest; one can’t ban them, any more than governments have succeeded in banning hartals.

Children playing soccer in the streets of Dhaka

In the streets of Dhaka by Debra Efroymson

I have often tried to argue that what is unimaginable is not a city without cars, but the existing cities that we live in, cities where the most dangerous daily activity for most residents is crossing the streets, where it is commonly accepted that dogs, children and others will be killed on a regular basis in the streets, where movement and parking of cars is considered a priority over the active play and independent movement of children and the socialising and mobility of the elderly.

How odd!

I was recently in New York City, where having walked about 40 blocks, my feet needed a rest just as I reached Times Square. I found an empty lounge chair and took a seat. Tourists were asking each other what was going on: “I just asked, they said nothing, they’re just sitting here.” No, not a staged event, just a piece of the street given over to a public use other than being stuck in traffic.

NYC June09 (32)

Time Square by Debra Efroymson

It was a gorgeous sunny day, and I sat for a long time, enjoying the lively yet quiet scene. It was a bit like a hartal in Dhaka, where the few cars are relegated to the margins and people reclaim the centre stage.

That big sign with the word “hope” on it might have said it all, but I would have chosen a different verb. We aren’t going to get there only by hoping…though those glimpses into the future may well give us the hope and courage to do what is necessary to make these extraordinary occasions into the blissfully mundane.

–Debra Efroymson

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Forgotten use of Streets


Each passing day it is more common to perceive the streets as obstacles – for traveling, resting, eating, meeting people, exercising, shopping – and ultimately living. After all, who wants to waste precious time in noisy, stinking and unsafe places like many urban streets? Not long ago it was different. The streets were not only used for transit, but also a daily living space for people; harboring lots of activities and having social functions.

It’s important to mention that we are talking about something different from segregated parks built with the purpose to provide a more ‘natural’ environment for walking and relaxing. These parks are not integrated with the rest of the city network. They have explicit boundaries and their own function. They aren’t incorporated in daily activities and in many cases they aren’t the best commuting routes.

One should not be forced to go to specific places to find peace and some fresh air. The whole city should be planned to offer places like these in the streets and areas that the citizens already use when they are going to work, school and other everyday activities.

Nowadays those uses for public space seem completely dissociated. Last week, I was biking to work after having lunch with my wife when I saw a friend of mine. The first thing he asked me was: “I didn’t know you were on vacation!” And he wasn’t the only one who asked me things like that. It is unconceivable to many people that you are really going somewhere (to work, to school, to pay your bills…) and at the same time you are enjoying doing it, exercising and meeting people. Commuting is supposed to be a bad time in your day; otherwise it’s not commuting. And there are many examples where municipalities, for the sake of safety and mobility, discourage any kind of use for the streets except linking A to B the fastest way possible. Ironically, that is exactly one of the reasons that we have to spend more and more time inside a car.

By driving, not only do you reduce your perception of your natural surroundings, but you also compromise conviviality and livability, especially in areas with heavy traffic. A friend once told me that when he worked for a company located in the Greater Curitiba, Brazil, an area (21km distant from his house) he knew at least 26 different paths to get there by bike. And along they way he was always discovering a new corner or square, without fearing getting stuck on traffic jams.

Streets can be great places, if we make them so…

Luis Patricio


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