People on motor bikes celebrate American President Barack Obama's visit to Kenya by holding up a photo, center top, of the president and First Lady Michelle Obama in Kisumu, Kenya, Saturday, July 25, 2015. President Barack Obama heralded Africa as a continent “on the move” Saturday as he opened a U.S.-sponsored business summit in Kenya, the East African nation where he has deep family ties. (Photo by AP Photo)

A Hawker Hurricane Mk XIIa 5711 (G-HURI) fighter aircraft prepares to perform an aerobatic display at the IWM Duxford on October 18, 2012 in Duxford, England. The aeroplane, similar to those that defended British shores during the Battle of Britain in World War II, is due to be auctioned by Bonhams in their sale of “Collectors' Motor Cars and Automobilia” at Mercedes-Benz World Brooklands on December 3, 2012. The plane was built in 1942 and joined the Royal Canadian Air Force the following year, where it remained for the duration of the war, it is expected to fetch up to 17 million GBP. (Photo by Oli Scarff)

A picture composed by the French street artist JR is plastered to a wall under a highway as part of a community project called “Through A Mother's Eyes”, which involves members of the economically distressed neighborhood of Hunts Point in images taken by and of themselves on June 30, 2011 in New York City. JR, a recent TED prize winner, has staged similar projects around the world that look to transform high crime and impoverished neighborhoods into spaces for street art combined with the celebration of community. (Photo by Spencer Platt/Getty Images)

A Fulton Hotshot lights a controlled burn on the so-called “Rough Fire” in the Sequoia National Forest, California, August 21, 2015. In California, suffering its worst drought on record, about 2,500 people were forced to flee Christian camps east of Fresno at Hume Lake as the so-called Rough Fire crossed Highway 180, officials said. (Photo by Max Whittaker/Reuters)

Justin Nelzen, in red vest, joins others as they work to rescue up to 70 horses along Cypresswood Drive near Humble along Cypress Creek, Monday, April 18, 2016, in Houston. More than a foot of rain fell Monday in parts of Houston, submerging scores of subdivisions and several major interstate highways, forcing the closure of schools and knocking out power to thousands of residents who were urged to shelter in place. (Photo by Mark Mulligan/Houston Chronicle via AP Photo)

A damaged vehicle is seen next to the ring road, around Skopje, near the village of Stajkovci, Skopje, The Former Yugoslav Republic of Macedonia, 08 August 2016. At least 21 people have died and more than 100 are injured in the heavy rain storm that hit the Macedonian capital Skopje late Saturday night causing severe damage to the roads and house infrastructure. More than 80 vehicles were hit by landslides at Skopje's ring road. The highway remains closed. The government announced a 15-day state of emergency in the Skopje and Tetovo region. (Photo by Georgi Licovski/EPA)

Pregnant Tibetan antelopes move across the Qinghai-Tibet highway in Hoh Xil, northwest China's Qinghai Province, May 29, 2023. A growing number of pregnant Tibetan antelopes are migrating to the heart of northwest China's Hoh Xil National Nature Reserve to give birth, according to the reserve's management office. Every year, tens of thousands of pregnant Tibetan antelopes start their migration to Hoh Xil in around May to give birth and leave with their offspring in late July. (Photo by Xinhua News Agency/Rex Features/Shutterstock)

“The Personal Urban Mobility and Accessibility (PUMA) is an experimental electrically powered road vehicle created by Segway and adopted by General Motors as a concept vehicle representing the future of urban transportation. It operates on two wheels placed side-by-side, a layout that differs in placement from motorcycles which instead have their two wheels placed at the front and rear”. – Wikipedia

The Project P.U.M.A. (Personal Urban Mobility and Accessibility) prototype is displayed for the media April 7, 2009 in New York City. (Photo by Mario Tama/Getty Images)