Although City Cars can work quite nicely as privately owned vehicles, they provide the greatest sustainability benefits when they are integrated into citywide, intelligently coordinated, shared-use mobility systems. The idea is to locate stacks of City Cars at major origin and destination points, such as transit stops, airports, hotels, apartment buildings, supermarkets, convenience stores, universities, hospitals, and so on. You just swipe a credit card, drive a vehicle away from the front of the stack, and return it to the rear of another stack at your final destination. From the user’s perspective, it’s like having valet parking everywhere.

City Car
Image: © Franco Vairani/MIT Smart Cities Project
City Cars can serve as intelligent agents, storing and providing energy to the power grid.

From the operator’s perspective, it’s a mobility service business. Success depends on having enough stacks and vehicles to satisfy demand, while minimizing unnecessary capacity and implementing an effective strategy for tracking vehicles through GPS and redeploying them, as necessary, from points of low present demand to points of high present demand. This system enables a high vehicle-utilization rate, doesn’t leave cars sitting uselessly around for most of the time—as private automobiles do—and minimizes the number of vehicles needed to provide a high level of personal mobility within an urban area.

This isn’t entirely new. The feasibility of shared-use, personal-mobility systems based on vehicle stacks in urban areas has recently been demonstrated by the Velo shared-use bicycle system in Lyon, France. Currently, this system is being extended to Paris with approximately 2,000 stacks and 20,000 bicycles.

Just as your electric toothbrush automatically recharges when you replace it in its holder, so City Cars automatically recharge when they are parked in stacks. Since they only need to travel from stack to stack, they don’t need long ranges or the associated bulky, heavy, and expensive battery packs that are, unfortunately, characteristic of today’s electric and hybrid cars.

Intelligent agents
When City Cars are stacked, they add storage capacity to the electric grid. They function as intelligent agents with the capacity to buy electricity from the grid when they need it and prices are low, and also to sell electricity back when they don’t need it right away and prices are high. In effect, they become active, alert traders in a dynamic electricity market. This helps the power grid to even out peaks, and allows it to make more effective use of renewable but intermittent power sources such as solar and wind. A project developed by Google and Pacific Gas and Electric, using plug-in hybrid cars, has already demonstrated (on a very small scale) the idea of vehicle-to-grid power.

Large-scale implementation of this concept would be a significant step toward transforming cities into distributed, virtual power plants—an Internetlike arrangement that promises many sustainability and security advantages. Buildings would not only consume electricity, but also produce it through various combinations of solar, wind, and hydrogen-fuel-cell technologies. Vehicles, and perhaps some buildings, would provide battery-storage capacity. The system would be coordinated through ubiquitously embedded intelligence and networking. Vehicles, appliances, and the mechanical and electrical systems of buildings would become intelligent economic agents, trading in energy markets with knowledge of demand and price patterns and the capacity to compute optimal buying and selling strategies.

The concept of intelligent agents operating cleverly in markets with dynamically varying prices can be extended, as well, to road space and parking space. Consider, for example, a citywide system that monitors traffic volumes in real time on a block-by-block basis, adjusts congestion road prices accordingly, and conveys this information to the GPS navigation systems of wirelessly networked City Cars. Drivers could then ask their navigation systems to find the quickest paths to destinations subject to cost constraints or the cheapest paths subject to time constraints. This produces a feedback loop controlling the allocation of road space: Vehicles adjust their routes in response to current price patterns, and price patterns adjust in response to vehicle densities.

We propose a similar approach to parking space. Using a simple sensing mechanism combined with wireless networking, City Cars can monitor the availability of parking stalls and stack space near their destinations. Based on instructions from drivers about the urgency of finding parking and the acceptability of some displacement from their destinations, City Cars might automatically bid in eBay-style auctions for available spaces and then guide drivers to them.

With our sponsor, General Motors, we have prototyped and demonstrated the feasibility of the crucial elements of the City Car system, and are currently exploring possibilities for implementing it in realistic contexts. A major exhibition on the City Car will open at the MIT Museum on September 28.

The City Car illustrates a general principle that, I believe, will become increasingly important in architecture and urban design as the technology of ubiquitously embedded intelligence takes hold and as designers recognize and respond imaginatively to its possibilities. Vehicles, appliances (both fixed and mobile), and the various mechanical and electrical systems of buildings will all evolve into specialized, networked robots that can make decisions and respond intelligently to the varying conditions of the larger environments within which they are embedded. Resources—particularly energy and space—will be managed and allocated in far more sophisticated ways than they are today. The effects on patterns of space use, building systems and their functionality, and the prospects for long-term urban sustainability, will be profound—often in ways that are, as yet, unimagined.