Unlike many concept cars, that throw practicality out the window in an effort to achieve fuel economy or light weight, the Hungarian-designed Antro Solo manages to fit three adults while returning excellent fuel figures and highway speeds.

Built almost exclusively from carbon fiber composite materials, the Solo weighs in at just 270kg. Seating is arranged like that found in the McLaren F1: the driver sits in the center, flanked by a passenger on each side. The light weight and hybrid design allow it to achieve fuel efficiency between 1.5L and 2.0L/100km (117-157mpg US) while also attaining a top speed of 140km/h (87mph). The car derives its power from a series of technologies, including solar power, human power and a standard combustion-electric hybrid system. The combustion engine is a small flex-fuel unit capable of running on petrol or ethanol, but the engine is only designed to be required for the longest trips the Solo makes. Short trips, between 15km-25km, can be made on solar power alone, thanks to the large array of high-efficiency solar panels stretched across the vehicle’s roof. The pedals in front of each passenger can also be used to power the generator, which stores the power in the car’s batteries, helping to keep the car in electric-only mode, reports the AFP. Once the human power is tired out, or when driving alone, the combustion engine kicks in to move things along.

Already built in prototype form, the car was recently displayed at the Budapest Museum of Transport for press and public viewing. Volume production is planned to begin in 2012, with the price of the Solo to start around €12,000 (US$18,000). A larger model, called the Duo and offering room for six but otherwise essentially identical, could follow. There are even plans to make the Duo capable of being split into two Solos with just 10 minutes of work.

The overall package is an impressive but dauntingly difficult combination of technology, design and innovation. If the company can in fact pull off mass production within four years, while meeting the necessary safety standards and still achieving its performance and efficiency specifications, and coming it at the projected price figure, the car will be a runaway success. But there will be no shortage of hurdles to clear along the way.

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Every major carmaker in the world has had its attention drawn, forcibly in some cases, to the issues of fuel efficiency, carbon emissions and sustainability. As the industry moves forward, these concerns are staged to take even greater importance in the overall design and planning of new cars. Mercedes-Benz has released an outline of how it will accomplish this task in the years ahead.

By applying technologies currently in existence and developing them further, Mercedes hopes to combine several angles of engineering and design to yield a line-up of efficient and green cars that still offer Mercedes’ trademark mobility and luxury. Under the BlueEFFICIENCY label, which includes aerodynamic upgrades, lightweight design and energy management and the BlueTEC label, which focuses on the mechanical improvements to be made, like forced induction, direct injection and smaller displacement engines, Mercedes will work to make conventional cars that place environmental sustainability at the forefront of design. The combination of these technologies can yield over 12% improvements in  Fuel consumption.

The company also has plans for hybrid drivetrains, zero-emissions battery-powered vehicles and cutting-edge combustion engine technologies that marry the best of diesel and petrol engine design, like Diesotto.

Mercedes’ F700 ‘research vehicle’ (pictured) equipped with a Diesotto engine has shown it can offer 238hp and 400nm of torque while still delivering fuel efficiency of 44.4 US mpg (5.3L/100km) on standard petrol. Carbon dioxide emissions are similarly low at 127g/km, about 20g/km higher than a significantly less powerful Toyota Prius Hybrid.

The company’s pure electric offerings are still in the distance, but its S400 BlueHYBRID is due for release in 2009, and will use high-tech lithium-ion batteries to help it achieve greater fuel efficiency while still remaining a suitable executive sedan.

The new S400 Hybrid will feature a 279hp (205kW) petrol V6 combined with a hybrid module delivering an additional 20hp (15kW) and 160Nm of torque. Fuel consumption is expected to average 30mpg (7.9L/100km) and CO2 emissions stands at 190g/km, which are quite low for the class of car.

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Toyota has earned its reputation for producing fuel efficient vehicles, but one dent in the Japanese automaker’s armor has been the gas-guzzling Tundra and Sequoia. To help rectify the situation, Toyota Engineers have been working hard on a 4.5L clean-diesel powerplant that will substantially improve fuel economy for the body-on-frame trucks. The 4.5L engine is reportedly scheduled to arrive Stateside by 2010, and it’s a no-brainer in light of the fact that both Ford and GM are offering similarly sized oil-burners for their trucks and SUVs.

You may remember the Dually Tundra fantasy truck that was shown last year at SEMA. Well, this news means the mega-sized diesel may not be far from reality. Inside Line is also reporting that Toyota may be delivering a monstrous 7.0L diesel for a commercial-grade Tundra, with a possible production date around 2011-2012. Toyota still hasn’t given the go-ahead for a heavy duty Tundra, so the king-sized diesel powerplant likely will arrive only if the larger Tundra does, too.

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Axon Automotive, creators of last year’s Eco-M super lightweight speedster, has entered the $10 million Automotive x prize with a new hatchback aimed at city dwellers. The new vehicle features a full carbon-fiber chassis and will likely be powered by a compact turbodiesel engine.

Keeping weight down will be a big consideration for the Axon hatchback as it strives to achieve the Automotive X Prize’s requirement for competitors to produce a 100mpg car. The UK based company has pioneered a special way of processing carbon fiber that involves engineers wrapping carbon-fiber braids around a foam core to produce a material that is as strong as steel but a fraction of the weight.

While there is no confirmation yet on the engine being used in the 100mpg hatchback, every measure is being used to make the car as aerodynamic and as light as possible - hence the rather dated looking rear-wheel covers. The final vehicle will be designed for both crowded cities and fast-paced highways and will be capable of seating two adults plus two small children.

Axon will be up against a number of strong competitors, including India’s Tata, which is developing two electric vehicles for the challenge, as well as Tesla and its famous electric roadster, and a Finish university that’s preparing a new electric sports car based on the Audi R8.

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Honda Accord Hybrid

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As we’ve heard before, the next generation of AMG-massaged Mercs will have to balance high output with low emissions. That means more turbos, less displacement and (gasp) hybrids.

The big and bad 6.2-liter V8 won’t be around much longer. Instead, AMG is turning its focus towards a new, twin-turbo 5.0-liter V8 that will produce 570 hp and 665 lb.-ft. of torque, with output possibly reaching 700 hp and 885 lb.-ft. to replace the outgoing 612-hp V12 mill.

Forced induction is only part of the equation, as AMG is looking to a new hybrid-equipped V8, dubbed BluePower, that will either come with the X-Trac Flybrid system or a 100-hp electric motor integrated into the transmission. There’s also talk that AMG will be releasing its own plug-in hybrid by 2012 and that diesels will continue to become an important part of the brand.

The other issue with which AMG has to contend is Mercedes’ own turbocharged offerings. Future M-Bs will be sporting turbo’d V8s displacing 4.0-, 4.6- and 5.5-liters, with outputs ranging from 355 to 544 hp.

And what of the upcoming AMG supercar? Car says that the gullwing super coupe, codenamed C197, will debut in March of 2010 and be powered by the same 6.2-liter V8 (likely the last application of that engine) while sending all that energy through an eight-speed automatic gearbox.

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The BMW X5 xDrive35d and 335d, both revealed live at the Detroit Auto Show, will be coming to the States in mid-October according to the latest rumor. The common engine will be BMW’s dual turbocharged 3.0L inline-six diesel, good for 265 hp and 425 pound-feet of torque. According to BMW, these two vehicles will be among the most fuel-efficient and best performing in their respective classes. In addition, with their urea injection system and particulate filters, they should be among the cleanest too.

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