Down these mean streets

MANY car designers are convinced that a radical change in automobile technology is going to be needed for the crowded megacities of the future. By 2030 more than 60% of the world's population is expected to be living in cities, up from 50% now, and more of them will be able to afford cars. The need to reduce emissions, an acute scarcity of land for roads and parking, and the prospect of laws restricting conventional cars all point to the idea that different and smaller types of vehicle will be in demand. With that in mind, some of those designers are coming up with things that look a lot like a vehicle that was familiar more than 50 years ago. Welcome to the return of the bubble car.

Bubble cars were built to provide cheap personal transport. Most were two-seaters with just three wheels. They became particularly popular when fuel prices shot up in 1956, during the Suez crisis. One of the first was the Italian-made Iso Isetta. Germany was a prolific builder, too. Messerschmitt and Heinkel, forbidden to ply their former trade of building military aircraft, turned to bubble cars as a peacetime alternative. BMW, meanwhile, re-engineered the Isetta to use an engine from one of its motorcycles.

Rising incomes, falling fuel prices and changing fashions did for the original bubble cars, but the idea seems ripe for revival and three new versions, known as EN-Vs (for Electric Networked-Vehicles), are enthralling the crowds at the Expo 2010 in Shanghai. They can be driven normally or operated autonomously, with their occupants doing other things while the cars automatically avoid bumping into one another. They can also be summoned from their parking places using a mobile phone. And instead of being powered by smoky little petrol engines, they are driven electrically. What is most intriguing, however, is that they balance on just two wheels.

The three EN-Vs, each with a different body shape, were built by a partnership between General Motors (GM), an American company, and Shanghai Automotive Industry Corporation, one of China's biggest carmakers. The two-wheeled balancing system the cars use was developed by Segway, a firm which makes personal-transport devices used by policemen, postmen and people who need to scoot around large corporate campuses (and whose owner, Jimi Heselden, was killed on September 27th when he rode one of the firm's devices over a cliff).

A balancing act

Riding a Segway personal transporter means gripping a set of handlebars while standing on a platform positioned between two wheels. The platform is kept in what Segway describes as a “dynamically stabilised” state. This is achieved by fitting each wheel with an electric motor that can rotate either clockwise or anticlockwise, as appropriate. A computer controls the resultant balancing act, using a series of motion sensors and gyroscopes. The upshot is that if the rider leans forward he travels forward, whereas if he leans backward the machine will stop and then go into reverse.

An EN-V is somewhat like a giant Segway, but without the handlebars. The platform, which contains the batteries and is mounted on a sliding mechanism, forms the chassis of the vehicle. It moves forwards when the vehicle is parked, so that it tips on to a pair of “landing wheels” at the front. That makes it easier to get in and out, for access is from the front via a large, transparent door—a traditional means of ingress for bubble cars. When the EN-V powers up, the platform shifts its centre of mass back to the centre of the vehicle. The drive wheels then rotate as necessary, to achieve both balance and propulsion.

The advantage of having only two wheels is that the car can be shrunk into a small package. At around 1.5 metres (59 inches) long by 1.4 metres wide, an EN-V is less than half the size of a MINI. Two wheels also allow greater manoeuvrability—an EN-V really can turn on a dime. With a top speed of 40kph (25mph) and a range of just 40km, its performance is limited. But average traffic speeds in many cities are already below 40kph and the EN-V's range is well within the typical daily mileage of most urban drivers, says Chris Borroni-Bird, GM's director of advanced vehicle concepts.

According to Dr Borroni-Bird, modern cars are over-engineered because they are designed for use between cities, not just within cities. In low-speed urban environments, he argues, lighter engineering can be used without compromising safety. In the case of the EN-Vs, that philosophy translates into bodies that are made from carbon-fibre composites and doors that are composed of polycarbonate plastics.

Automated driving, moreover, takes the EN-Vs to a new level of sophistication. The satellite-based global-positioning system provides each vehicle with its location on the Earth's surface, to within a few centimetres. Other sensors establish its position on the road and in relation to the rest of the traffic. These sensors include infra-red detectors, which can recognise people and animals from their body heat (and which are already available in some cars); short-range ultrasonic scanners to detect nearby objects when parking; long-range radars to check the road farther ahead; and optical systems that are trained to recognise certain objects, such as cars, motorcycles, traffic signs and road markings.

Some of the tricks used by EN-Vs come from systems developed by researchers at Carnegie Mellon University, who used a modified GM Chevrolet Tahoe to win the 2007 Urban Challenge. This was an event staged by America's Defence Advanced Research Projects Agency to find vehicles that could operate autonomously alongside other traffic in a city and perform complex manoeuvres while doing so.

The other thing that EN-Vs can do is talk to each other. So if, for instance, one EN-V detects another by radar, it can check what that other is intending to do and agree on how to pass it safely. Such communication also allows for “platooning”, with one or more EN-Vs tagging along automatically behind a leader. That is a way of providing extra seating for a family outing, say, or of carrying luggage that will not fit in the leading vehicle.

Day-to-day automated driving of this sort is, Dr Borroni-Bird admits, far into the future and may well require new infrastructure on the roads. But in the near term he believes it is possible to take steps towards it. The automated valet-parking feature on the EN-Vs could, for instance, be used off public roads at places like shopping centres. Drivers would pull up at a designated entrance, get out, and leave their vehicles to trundle off and park snugly by themselves in a high-capacity car park. A phone call at the end of a shopping expedition would summon the car back.

I'm forever blowing bubbles

Nor is the EN-V the only bubble car on the drawing board. Gordon Murray, who designed racing cars for McLaren, and also its 370kph road car, is developing two tiny four-wheel cars, one with a 660cc engine and the other with an electric motor whose batteries give it a range of about 160km. These cars can carry three people, with the driver sitting in the middle and passengers behind. The single door hinges forwards and upwards, so such cars can be parked facing the pavement and close together—indeed, three of them can sit abreast in a standard parking place.

Mr Murray's idea is not just to produce vehicles that have a low impact on the environment but also to use a green (and cheap) manufacturing system to build them. By doing away with big, heavy metal presses and assembling the vehicles from a simplified tubular chassis, he thinks the cost of production could be cut to about a fifth of that in a typical car factory. He is hoping to license both the design of the cars and their production process to other carmakers.

Renault, which is launching a range of electric cars, is also sticking to four wheels for its smallest design, the Twizy. This will be seen at the Paris Motor Show, which opens on October 2nd, and is due to go on sale in 2012. It will have a top speed of 75kph and a range, with a full battery, of just under 100km. Inside, the driver and a single passenger sit in tandem, as they would on a motorcycle. Outside, the body is made almost entirely of clear plastic—the ultimate bubble car, perhaps.