Transport has a lot to answer for when it comes to harming the planet. While cars and trains are moving towards greener, electric power, emissions from air travel are expected to increase massively by 2050. If we want big green sky solutions, we need blue sky thinking Fortunately, there's plenty of that happening right now, particularly the short-haul flights powered by batteries.

Harbour Air is the largest seaplane airline in North America, flying 30, 000 commercial flights in 40 seaplanes each year. Significantly, all Harbour Air routes last less than 30 minutes, making it perfectly fit for electric engines. “As an airline, we're currently in the process of turning all our planes into electric airplanes. says CEO Greg Mc Dougall. To make this happen, the airline has partnered up with MagniX to create the worlds first commercial flight with an electric engine.

Making the skies electric isn't just good for the environment, it also makes sound financial sense: a small aircraft uses $400 on conventional fuel for a 100-mile flight, while an electric one costs $8-12 for the same distance, and that's before you factor in the higher maintenance costs of a traditional engine. There's also the added bonus that electric planes are just much more pleasant to fly in. No loud engine noise, no smell of fuel, just environmentally friendly peace and quiet.

While there has been real progress in the e-plane industry, the technical challenges that remain are keeping everyone's feet firmly on the ground. A battery, even a lithium one, only provides 250 watt-hours per kilogram; compare this to liquid fuel, which has a specific energy of 11, 890 watt-hours per kilogram. Carrying adequate batteries, however, would make the plane too heavy to get off the ground. In aircraft, where every bit of weight counts, this can't just be ignored.

The transition （过渡） from gas to electric in the automobile industry has been made easier by hybrids-vehicles powered by both fuel and electricity. Many believe the same pattern could be followed in the air. Fuel consumption could be reduced as the electric component is switched on at key parts of the journey, especially on take-off and landing.

It's certainly an exciting time for electric flying. With companies like Harbour Air taking the lead, battery-powered planes, especially on short-haul journeys, are set to become a reality in the next few years.

The ride-sharing company Uber has removed its self-driving cars from the streets of San Francisco, California. The action came after a dispute between Uber and state officials over whether the vehicles needed special permits to operate.

Uber recently launched testing of its self-driving service in San Francisco. But shortly after the launch, California's Department of Motor Vehicles (DMV) told the company to stop the self-driving vehicles. State officials said the Uber cars needed the same special permit given to about 20 other companies testing self-driving technology in California. Uber argued that its technology does not make vehicles fully autonomous, and so the special permit was not needed. It added that all of Uber's "self-driving" cars have a driver sitting in the passenger seat to take over if needed.

The head of Uber's self-driving technology, Anthony Levandowski, explained the company's position in a blog post. He said the self-driving Uber vehicles do use high-technology tools to assist drivers. But they are not fully autonomous and require a driver to be at the controls at all times. He compared the technology to solar carmaker Tesla's advanced driver assist tools. Telsa's Autopilot system allows its cars to steer in a lane, change lanes, and speed up or slow down based on nearby traffic. The company tells drivers that, when using Autopilot, they should still always be ready to take control of the vehicle. Vehicles equipped with these high-tech driver assist tools do not need a special permit to operate in California.

It's hard to understand why the DMV would seek to require self-driving Ubers to get permits when it accepts that Tesla's autopilot technology does not need them," Levandowski wrote. San Francisco's mayor, Ed Lee, praised the DMV for stopping Uber's self-driving vehicles. He said he supports self-driving development and testing. But only under conditions that put human bicyclists' and pedestrian safety first."

In the United States，a company is working on a project that could change the way we think about public transportation.Its planned system would move people around in steel tubes.Those passengers would be traveling at speeds of up to 1,200 kilometers per hour.

The futuristic steel tube transportation system is called Hyper1oop.Workers plan to test the system next year in a specially built community called Quay Valley.The town will be powered entirely by energy from the sun.

The Hyperloop transport system is the idea of businessman Elon Musk.Dirk Ahlborn is head of Hyperloop Transportation Technologies.He says his company has taken Mr.Musk’s idea and is developing a system that will be safe，environmentally friendly and fast.

“It’s 100 percent solar powered…we’re not going to get up to 760 miles per hour，but we believe we can actually break the records that are existing right now.”

This means that a four-hour drive from Los Angeles，California to Las Vegas，Nevada，could someday take only 30 minutes by Hyperloop.The system involves a series of capsules that float inside a long tube.These containers would not need to travel along a pathway or track.The system has been designed to operate above or below ground.

“Inside the tube you create a low pressure environment very similar to an airplane that’s at high altitudes.So now the capsule travelling inside the tube doesn’t come up against as much resistance，and therefore can travel really fast with very little energy.”

Dick Ahlborn and his company will use an eight—kilometer track in Quay Valley to find the best way to set up passenger traffic and repair capsules.A larger system will cost an estimated six to $10 billion to build.If Mr.Ahlborn and his company succeed，we may one day see these very fast Hyperloop capsules speeding through tubes around the world.