This page is a summary of Franco Vairani's doctoral dissertation at MIT, in the department of Architecture, for the Design and Computation program. It presents a proposal for urban transportation based on the design of a small collapsible vehicle.

The work was done under the supervision of Professor William J. Mitchell, and the design developed in collaboration with the Smart Cities group at the Media Lab.

Car and the city  

Problems associated with the massive adoption of automobiles have become the center of a world-wide debate. While it seems inevitable that upcoming technologies will eventually develop a sustainable solution to the environmental concerns (pollution, depletion of energy sources), cities will continue struggling to accommodate the increasing number of cars because of one simple reason: space is limited.

Although every developed country has built important infrastructure in the form of roads, highways, parking lots and garages, the massive vehicular infrastructure developed in the U.S. to support this lifestyle created distinct urban patterns. Living near the city center was no longer a necessity because it was assumed that the car would provide with immediate transportation to any destination whenever required. The process makes residential zones shift to the outskirts, creating sub-urban areas. In turn, as urban sprawl moves residential areas to distant locations, there is a deterioration of the city centers. Wider streets and parking lots start replacing valuable land, and the migration of shopping and recreational activities to the suburbs make walking around downtown areas less attractive.

The statistics are remarkable: in 2001, 92.1% of the U.S. households owned at least one vehicle, and over 60% owned two or more vehicles. [2]. The use of transit systems rapidly declines and becomes unsustainable in urban areas with low density and high automobile dependency. In many cities in the U. S., transit barely covers 1% of all the travel needs, and even New York, with the most comprehensive public system of all US cities, it only reaches to 11%. In contrast, European cities, on average, satisfy 23% of all passenger transportation needs by transit.

Intersection of I-10 and I-405 between Los Angeles and Santa Monica. [Source: Google Earth]
Car trouble  

Without negating the benefits of personal mobility, one must also recognize the incongruence of the current configuration of the automobile. Check these numbers: The average American driver drives 29 miles each day. 88% of drivers in the US travel less than 80 miles daily, and for over 40% of drivers, their total travel distance (usually including a round trip) is less than 20 miles. [5]

At the same time, in 1990, the U.S. Census Bureau reported that the average vehicle occupancy was 1.1 passengers per car, in trips from home to work. The number is slightly better for shopping and other family or personal business (around 1.7 and 1.8 respectively).

An average car weights around 3000 lbs; if it carries only one person at 150 lbs, the person represents only 5% of the total weight, which means that approximately 95% of the energy required to move forward is spent on moving the car itself.

On top of that, the average automobile spends 95% of its time parked -that is, unused- while there are three other parking spaces
unoccupied per vehicle.

These inefficiencies multiplied by the staggering number of vehicles in circulation have resulted in huge energy losses, pollution and vast portions of the city lost in support systems for the car. In the U.S. alone, there were 250,851,833 vehicles registered in 2006 [6]. If we consider three parking spaces per vehicles at 200 square ft per
parking stall, the total area would be 5280 square miles, equivalent to the size of Connecticut. UCLA Urban Planning professor
Donald Shoup reveals the fallacy of the car parking status quo in his book The High Cost of Free Parking. When cities make parking requirements for any kind of development, they effectively bundle the cost of parking spaces into the cost of the new construction. This makes driving more affordable but everything else, such as housing, more expensive, not only by adding one cost to another but also by restricting the available space for housing, commercial and other

Thinking outside the 3 boxes  

The argument of this work is that these problems are partly the result of an outdated set of design premises for the automobile which have barely changed since cars appeared in the late 1800’s. The work discussed here proposes a different approach to urban transportation, by combining the advantages of mass transit with the convenience of personal mobility.

This work started in 2003, when Prof. William J. Mitchell organized a research team to explore new ideas for vehicles in the future. The goal was to re-think the car as a design object and redefine the relationship between people, cars and cities. Prof. Mitchell gathered a multidisciplinary team of people to participate in a workshop, with backgrounds as diverse as urbanism, architecture, industrial design, mechanical and electronic engineers, as well as software programmers. The workshop offered a blue sky to study any kind of ideas related to the future of transportation, far from the constraints of the automotive industry. Over several semesters, the group produced a large number of concepts -not all displayed here- which ranged from performance vehicles to communication devices and mechanical components.

The workshop was hosted by the Smart Cities group at the MIT Media Lab, where General Motors is a sponsor. Representatives of GM participated actively in the workshop as guest critics.

Robot Wheels  

Early on, students Patrik Künzler and Peter Schmitt started working on the idea of packaging the critical functions of the car into the space of the wheel.
The development of the robot wheel would be a critical contribution to the group. Many concepts in the workshop -including the bit car- would incorporate two or four robot wheels in different configurations to create new designs.

In short, these Robot Wheels are modular elements that eliminate the need for a traditional engine block, and provide the vehicle with all necessary functions to move. Each wheel includes an electric motor, steering, braking and suspension. The operation of the vehicle is possible through a number of microcontrollers that respond to a central computer. The CPU of the car translates the input of the driver into the necessary actions that each wheel has to take to accomplish the goal.  This is known as a drive-by-wire system, since there are no mechanical linkages between the driver and the wheels that move the car.

Crumple zone  

I teamed up with William Lark Jr. again with the objective of creating a different kind of car. Most cars are designed for driving; our car, instead, would be designed for parking. The exercise was meant to explore possible solutions for parking arrangements and deliberately ignored other constraints. The vehicle needed to be capable of carrying at least one person and reduce as much as possible the space requirements when not in use. The obvious references came from space-saving structures found in everyday objects, more specifically from collapsible and stackable designs. These structures have some kind of adaptation that transforms their volumetric needs either as a single object or in a group.

The first iteration was just an open cabin for a single passenger. The design was bulky and left many issues unresolved. However, it clearly explained the concept and showed the potential of this idea.

(1mb - Quicktime)

Collapsible design    

Although the idea of a stackable a car might appear unusual at first, collapsible designs are extremely common in every day objects.

Collapsible designs re-distribute the impractical volume occupied by an object in some other way. Naturally, unless the object is physically compressed, the volume of the artifact itself does not change, it is just redistributed so that it takes up less useful space or provides additional functionality to the product. (Mollerup 2001)

Collapsible design is usually a combination of different strategies. Books are best read when open, but they close (collapse) when stored. When they are open so that we can read, books are horizontal bodies (like cars), but nobody thinks of organizing a library like that. Instead, they are closed and placed vertically so that they take as little space as possible. However, we like keep our unused cars in the most inefficient position possible, taking up valuable space from the city.

    F/A 18 fighter jets with folded wings aboard the aircraft carrier USS Dwight D. Eisenhower [Source:]
Bit Car  

The design was sketched directly into 3D software capable of linking all the parts into a kinetic structure. This allowed to study the adequate placement of joints and the size and shape of each element so that they do not get in conflict with the folding mechanism. Unlike the first design, which only achieved space savings by overlapping units into each other, this collapsing mechanism has two strategies for gaining space: lifting the car up at a certain angle already reduces the footprint of each vehicle, but the same technique creates the space necessary for another unit to overlap a certain distance and further augment these gains.

The external frame is split in two major parts, joined by a hinge point approximately in the middle of the vehicle. The main structure grabs the front wheels and the passenger unit, while the smaller frame only connects the rear wheels to the rest of the car. The pivoting mechanism is simple. The rear wheels simply move forward while the front wheels are locked in place, thus pushing both movable components of the chassis closer to each other. Since both elements have rotational joints at the ends and one in the middle, the force applied in the structure pushes the middle articulation upward, and this movement tilts the cabin accordingly.


Bit cars are this: small electric vehicles for one or two passengers, to be used in short distance trips in urban areas. They have the ability to collapse and interlock with another similar unit when not in use. The ability to stack also suggested the creation of a fleet of vehicles for shared used, similarly to the way shopping carts are used in a supermarket. Users do not own one car in particular; they are members of a program by which they have access to a vehicle when they need one. These stacks act as “car dispensers”, so people who need personal mobility simply pick the first vehicle from the stack and drive away. When they reach their destination, they return the car to the back of another stack.

(4mb - FlashVideo)

The CityCar proposes a completely different organization: a shift from a product-based to a service-based scheme. That means, drivers do not have to face a large investment upfront to obtain personal mobility; instead, they pay for the use of the transportation service only (just like buses or trains).

The use of “robot wheels” also has two other important advantages. As demonstrated in Peter Schmitt’s work, these wheels can be designed as modular units, with a standardized interface so that they can be mounted them directly to the frame. Perhaps more importantly, they are capable of providing omnidirectional movement to the car, which results in substantial gains because it eliminates the space requirements of a conventional maneuvering.    
Double parking  

Based on the available data, results indicate that such a design could potentially reduce the actual space requirements for a car dramatically. In a typical situation, bit cars can compress to a ratio of approximately 1:3.5 in a standard curbside parking arrangement. That is, three and a half bit cars fit in a regular parking stall of 8’6” x 22”. And the space savings are even higher for off-street parking (lots and garages).

The comparison, still, is not entirely fair, because bit cars are shared, and traditional automobiles are not. That means, that when a user leaves a bit car in a stack, and after it is fully charged, someone else will take it for a spin again before the first user needs to use a bit car again. A study by the Transportation Research Board in 2005 concluded that one vehicle in a car-sharing program takes 14.9 privately owned cars off the street. Assuming the data of the TRB is accurate, then the ratio jumps to 74:1.

To illustrate the consequences of this, I have taken one block from downtown Houston, TX, located between Main street, Bell street, Travis street and Clay street, which is currently devoted entirely as a surface parking lot. The block is 250 feet on each side, with a usable area of 62500 sq feet. Inside it, there are 260 stalls, so each vehicle takes up about 240 sq feet, which is a very good efficiency rate for a parking layout.
With a full fleet of bit cars in Houston, this block could be entirely redesigned with bit cars in mind and almost entirely reused to create green spaces, skyscrapers, shopping or recreational areas or anything that urban planners and themarket can imagine. Four stacks, each with 17 bit cars have been moved next to the side streets (no need to store the vehicles deep inside the block), making a total of 68 bit cars, which would replace all the parking spaces in the original diagram. The entire block would regain 60,725 sq feet out of 62,500 sq feet (97% of the land) for other purposes than parking and still fulfill the spatial needs of storage of units for personal mobility.
Current landscape in Houston, TX [Source: Google Earth]   Same block with comparable parking requirements for bit cars.

Car-sharing has already been greatly enhanced by the use of so-called intelligent transportation technology (Barth, Todd, Shaheen 2003). All bit cars would be integrated to the information network of the city, so that the management has real-time information on the distribution and movement patterns of city cars. This information can then be extended to the users. A user with a handheld information device is then able to know which is the closest stack with cars, fully charged and available to drive. The same electronic systems could be used for fare collection.

This design is not a one-fits-all solution. Bit cars are intended for a specific purpose: most daily trips within a city. They are no good if you need to purchase a new sofa. Furthermore, cities have evolved differently and created distinct requirements. For example, low-density urban areas such as Los Angeles are characterized for longer distances in the average trip, so the design of a Citycar there may require a greater range and thus a bigger battery.

We do not think there are significant hurdles in the implementation of a project like the CityCar. In terms of technology, almost everything seems feasible. Probably the weakest, unresolved issue to date is a convincing method for recharging these batteries.

Perhaps the only real obstacle to adopt such a system has to do with the cultural significance of the automobile. For over 100 years, we have come to assume that cars are private property, and they carry a strong meaning in addition to their functional role. It would require a cultural shift to accept that cars may also work as common goods, just like a bus or a train. I have deliberately chosen to ignore these
aspects when developing this project, but they still exist and could become a decisive factor for success.

However, the potential is there. A new approach to urban mobility could have huge consequences in the shape of our cities and in the way we live in them.


My work together with the Smart Cities group has been featured in hundreds of publications in the U.S. and across the globe. In 2006, I.D. magazine recognized the bit car in its Annual Students Review awards. In 2007, Time Magazine selected it as one of the Best Inventions of the year. Other publications include Business Week, Fast Company, Esquire, Discover, National Geographic Kids, Architectural Record, Metropolis, The Washington Post, The Boston Globle, Le Monde, The Guardian, El País, Clarín, Veja, Interesection, to name a few.

The bit car has also been included in the Warner Bros. documentary The 11th Hour, and in TV shows for CNN, BBC, Fox News, CBS News, the Discovery Channel, Sundance channel, among others.

Additionally, my designs have been exhibited at the 2007 Venice Biennale, and featured at the UN Symposium for Climate Change in Oslo, as well as the MIT museum, Musée de la Civilisation, and other museums in the US and Canada.

©2003-2009 Massachusetts Insitute of Technology
©2003-2010 Franco Vairani. All rights reserved.