Sustainable Urban Mobility in 2020

To make the car of the future, we need to make the city of the future, says MIT designer Ryan Chin.

How can you design a city by designing a car? Today’s automobiles are driven by an increasing number of users who live in cities. The United Nations reported in 2007 that migration patterns and population growth have created an equal split between inhabitants of cities and rural areas for the first time in human history. This general trend will continue for the next several decades and will produce a very urbanized world.

In 1950, New York City was the only megacity on the planet, with 10 million occupants. Today, there are 25 megacities that are mostly in developing countries. To verify this trend, we need only to look at the rapid urbanization in China to see the mass migration of the rural poor to urban areas for economic opportunity. Population experts project that most of the urban growth will occur in Asia and Africa for the next several decades. Simultaneously, humanity’s thirst for personal mobility will continue to grow. History shows that, as countries develop economically, so does their use of four-wheeled motorized transportation.

The world’s automobile fleet is currently estimated at 800 million cars that serve the 7.8 billion people living on Planet Earth. In the developed world, roughly seven out of 10 people own a car, whereas in the developing world, it’s two out of 10. The continued economic development of Brazil, Russia, India, and China will fuel the growth of this fleet to more than 1 billion cars by 2020. The continued use of this personal transportation model is simply unsustainable given the combination of energy inefficiency, environmental consequences of fossil-fuel usage, potential disruptions to fuel supplies, urban sprawl created by automobile reliance, and congestion caused by inadequate alternative modes of transport. What we need is to radically rethink the problem by examining not only the automobile itself, but also how it is used in cities (where most of us are currently living).

Size and Weight

2010: Today’s automobiles weigh an average of nearly 4,000 lb, approximately 20 times the weight of the driver. Today’s automobiles also have a footprint of approximately 100 square feet, which is nearly 15 times the amount of space required for a comfortable office chair. But the size requirements don’t stop at the footprint of the vehicle, if we consider the space that cars occupy on the road, in parking at home, work, and other destinations; add to that the space for maintenance and repair and it quickly grows to approximately 1,200 sq. ft. per vehicle. In midtown Manhattan, a 1,200 sq. ft. condominium would cost you upwards of $2 million to own.

2020: Tomorrow’s automobiles will be more lightweight and smaller. Size, weight, and energy efficiency are three factors that intimately interconnect in the design and engineering of automobiles. The lighter the vehicle, the more energy efficient it will be to move the mass of the car. The smaller the vehicle, the less mass you have. This set of relations forms a set of positive and negative feedback loops that ultimately affect the design of the vehicle. It will be imperative to incorporate technological improvements in lightweight materials, and composites will certainly help to make vehicles leaner, but this is not enough. Vehicles must also become more compact. These changes will not only improve energy efficiency, but also the vehicles’ overall footprint.

Range and Speed

2010: Today’s automobiles have a fuel range of about 300 miles (meaning they can travel 300 miles or so on one tank) can go from 0 to 60 mph in less than 10 seconds, and top out at more than 110 mph. This is great for intercity travel, but most Americans don’t travel that far. More than 80% of daily commutes in America are less than 40 miles (round trip). With more than 81% of Americans living in metropolitan areas, you simply don’t need to go 100 miles an hour down a city street. If you travel to Shanghai today, the average speed in the city is 9 mph. Bangalore, India, has achieved 24-hour congestion. Today’s vehicle is simply over-engineered for most practical purposes in cities.

2020: Tomorrow’s automobiles will not need that much refueling autonomy. BMW recently finished a series of user experiments to examine “range anxiety” — the fear of running out of electricity in electric cars — and discovered that their new electric mini (with 100 miles of range) has two to three times the range required for practically all trips. Users don’t need to have five to six times the range, and they quickly learned to adapt to the constraints (and benefits) of this new vehicle type. The introduction of electric charging infrastructure in the upcoming decade will virtually eliminate range issues in urban areas. Cities like San Francisco, Portland, Paris, Madrid, and Barcelona all have initiatives to bring a network of charging stations in their respective metropolitan areas. Car makers are introducing plug-in options for many models that enable the electrical charging from a common 110V household outlet.

Gasoline versus Electric

2010: Today’s vehicles are predominantly powered by petroleum-based fuels. An internal combustion engine is terribly inefficient (approximately 15%) in converting chemical energy into mechanical work to drive the wheels of your car. Hybrid vehicles are better at conserving energy at the cost of a more complex powertrain, but projections for the next five years call for less than 12% of the total new car market. The remaining alternative fuels, like compressed natural gas, hydrogen, compressed air, and biofuels, have varying levels of efficiency, but are utilized in even fewer numbers than hybrids. Battery electric vehicles utilize electric motors that are more than 90% energy efficient, but these have not taken over mainstream markets because of limitations of battery technology.

2020: Tomorrow’s automobiles will be increasingly electrified. The emergence of new battery chemistries such as lithium ion nanophosphate have allowed battery manufacturers to produce cells that have higher energy density and lower internal resistance, thus allowing rapid charging in less than 30 minutes. In fact, my colleagues at the MIT Electric Vehicle Team have been able to rapid-charge these new cells in less than 7 minutes with just a 10% degradation in capacity after 1,500 cycles. For comparison, lithium ion cells in your laptop today have roughly 1,000 cycles of usable life. The ability to rapid-charge will enable users to top-off their batteries in about the time it will take to order and drink an espresso, thus opening up new opportunities to create a ubiquitous charging network distributed throughout cities. No longer do we need to charge only at home or the workplace where our cars sit waiting for six to 10 hours.

Driver-Controlled versus Autonomous Driving

2010: Today’s cars are driven by human operators. Drivers have a number of telematic devices that aid in driving, such as antilock brakes for safe stopping, adaptive cruise control for the highway, parking sensors to help avoid scratches to the bumpers, and GPS for navigating unfamiliar places. However, we still have more than 50,000 deaths a year in the United States under the current driving paradigm. Today’s drivers sit in traffic for more than 50 hours a year and endure the stop-and-go driving experience.

2020: Tomorrow’s cars will be increasingly autonomous. The annual DARPA Urban Challenge has consistently proven to be a tremendously useful catalyst for innovations in autonomous driving. The most recent challenge shows that autonomously driven vehicles can navigate in busy city streets without incident. The potential of autonomous vehicles to self-drive and coordinate with other autonomous vehicles is to smooth traffic flows. In urban environments, top speed is not necessary; it is the orchestrated movement of vehicles within a speed regime that will improve congestion. The introduction of semi-autonomous systems such as self-parking and automated highway systems has provided useful lessons in the benefits and challenges of autonomous driving. Continued federally funded research in this area, combined with improvements in computational power, will enable the miniaturization of autonomous technologies, thus making autonomous driving commercially viable for mass markets in the coming decade.

Private versus Shared Ownership

2010: Today’s automobiles are designed for private ownership. The burden of ownership includes the cost of the vehicle, depreciation, tires, licensure, taxes, registration, insurance, maintenance, fuel, and parking. These individual direct costs are compounded by what economists call “negative externalities,” which include congestion and pollution leading to global warming — that is, costs to society not immediately felt by the individual user. Privately owned commuter vehicles that may drive two hours a day (round trip) will sit doing nothing useful for 92% of the day. During this state, the car takes up valuable real estate and doesn’t move people around. Single passenger occupancy also doesn’t help in this situation; if I stand on Memorial Drive in Cambridge, Massachusetts, I could wait up to 20 minutes before seeing a vehicle with two occupants. In that same city, approximately one-third of the land area is devoted to the servicing of automobiles (this includes roads and parking for cars) that are principally used by private individuals. This is not an atypical land-use percentage devoted to the automobile throughout the United States.

2020: Tomorrow’s automobiles will be increasingly utilized in cooperative or shared-use models. The emergence of car-sharing and bike-sharing schemes in urban areas in both the United States and Europe have established alternative models and markets for fractional or on-demand mobility. Zipcar, the world’s largest car-share program, has grown from just a handful of cars to a fleet of 6,000 cars and 275,000 drivers in 49 cities in just under 10 years. It’s very difficult to own one-quarter or one-tenth of a car with traditional ownership, and let’s not even talk about fractional insurance. Shared ownership provides users fractional ownership that allows them access to any vehicle in the fleet whenever they please and for as long as they need, just like video on demand or print on demand.

Radical Rethinking Required

Since 2003, the Smart Cities group at the MIT Media Lab has developed solutions to directly tackle these problems. We have designed an electric two-passenger vehicle called the CityCar, which utilizes in-wheel electric motors called Wheel Robots that have incorporated drive, suspension, and braking directly inside the wheel. Each wheel is independently controlled with by-wire controls (no mechanical linkages) and is capable of 120 degrees of steering, which provides very high maneuverability. The CityCar can turn on its own axis (zero turn radius) and can make sideways turns by turning the wheels perpendicular to the primary driving axis.

The Wheel Robots eliminate the need for traditional components like drivelines, transmissions, and gearboxes. We have taken advantage of this freedom by rethinking the architecture of the vehicle. Since there is no driveline, we can make the vehicle very compact by folding the chassis. The CityCar can fold up to half its length to just under the width of a traditional parking space. The CityCar, when folded, is less than 60 inches in length and 100 inches when unfolded (comparable to the Smart Car). Three CityCars when parked can fit into one traditional parking space. It weighs just 1,000 lb, thus making it very lightweight and energy efficient, and the new architecture allows us to rethink entry and exit. We have designed a front ingress solution that easily allows the driver and passenger to safely exit the vehicle onto the curb rather than the street. The folding mechanism complements this feature by articulating the seats so that the user can ergonomically and elegantly exit at an elevated position. CityCars are designed to park nose-in to the curb, which allows the users to use the sidewalk rather than the street. Finally, the in-wheel motors will provide plenty of low-end torque, thus making the CityCar fun to drive in urban areas.

Simply redesigning the vehicle is only one part of the solution. We have also created a new use model, called “Mobility on Demand”(MoD), which utilizes a fleet of lightweight electric vehicles (LEVs) that are distributed at electric charging stations throughout a metropolitan area. The LEVs are designed for shared use, which enable high utilization rates for the vehicles and the parking spaces they occupy. The use model mimics the bike sharing systems made popular in Europe, whereby users simply walk up to the closest charging station, swipe a credit card, pick up a vehicle, drive to the station closest to their destination, and drop off the vehicle.

Our group has designed our CityCar to fit into these MoD systems, thus creating a complementary network that can solve what transportation planners call the “First Mile Last Mile” problem of public transit — that is, how to bridge the distance between your real origin (i.e., your home) to the transit station and from the transit station to your real final destination (i.e., your workplace). Often these distances are too long to walk, thus encouraging private automobile use.

The expansion of MoD into a sustainable urban ecosystem can be achieved by introducing additional shared-use vehicle types like electric bicycles and scooters. (Smart Cities has also designed an electric folding scooter called the “RoboScooter” and an electric bike called the “GreenWheel.”) This will offer flexibility and convenience while allowing for asymmetric trips. For example, a user can drive a GreenWheel to the supermarket, then go home with a CityCar that can carry groceries.

We believe that MoD systems will work better than private automobiles in cities because you never have to worry about storing the vehicle. In many cases, a MoD charging station will be closer to your final destination than if you had to park in a private lot. A typical urban trip is short, however; much of the time spent is not actually driving, but rather walking to the vehicle and finding parking once you get there. A recent study by the Imperial College in London showed that, during congested hours, more than 40% of total gasoline use is by cars looking for a parking space!

In 2020, I expect the shift from private gasoline powered use to shared electric vehicles will be on its way. There are three primary factors that will accelerate this trend:

1. Economic and environmental pressure to transition away from petroleum fuels.

2. Technological innovations.

3. Political leadership to promote new regulations and policies for this type of innovation.

In 2010, China has become the world’s number-one automobile market, surpassing the United States. in the total number of cars purchased. The increased consumption of fossil fuels and the emissions of CO2 will be part and parcel of this economic development. This will all but guarantee increased demand for petroleum and set the stage for political responsiveness.

Luckily, most of the technologies required to make the CityCar real already exist today, such as highly efficient electric motors, computational horsepower, new battery technologies, wireless network communications, lightweight composite materials, advanced sensing, and GPS. The only thing that limits us is the inherent difficulty of breaking away from our preconceived notions and embracing this radical rethinking.

About the Author

Ryan Chin is PhD student at the MIT Media Lab in the Smart Cities research group. He has led and managed the design development of lightweight electric vehicles (LEVs), including the CityCar, RoboScooter, and GreenWheel electric bicycle. In 2007, Chin co-founded the MIT Smart Customization group, which is focused on improving the ability of companies to efficiently customize products and services across a diverse set of industries and customer groups. Web site:

The author would like to acknowledge the collective effort of the Smart Cities team that developed the CityCar, RoboScooter, GreenWheel, and the Mobility-on-Demand System. He is particularly grateful for the guidance of Professor William J. Mitchell and team leaders William Lark Jr., Raul-David “Retro” Poblano, Michael Chia-Liang Lin, Andres Sevtsuk, Dimitris Papanikolaou, and Chih-Chao Chuang.