Having the handle bars at the side looks weird – surely it must feel unnatural and unstable?

With a bicycle you stretch forward to reach the handlebars – there is nothing inherently natural about that, it is just what you are used to. The upright position on a YikeBike is remarkably comfortable and safer too because it is easier to both see and be seen. At a top speed of 20 kph you are never going fast enough for wind resistance to be an issue (and the electric motor is doing the hard work anyway).