Hugely popular with children, fatbikes -- so called for their ultra-thick tyres -- are electric bikes that look like squat motorcycles and can reach speeds of up to 60 kilometres (37 miles) per hour.Competing for space on busy cycle paths in the famously flat Netherlands, many classic cyclists see fatbikes as a menace due to their superior speed and size.Complaints of "fatbike gangs" of youths tearing around Dutch cities and causing havoc are also commonplace.A petition against "aggressive fatbikers" in Amsterdam has garnered 2,400 signatures, complaining: "Pavements are racetracks. Public space no longer feels safe."So city authorities have decided to ban them in the Vondelpark, a busy park that attracts locals and hordes of tourists on hire bikes or roller skates."We get a huge amount of complaints," said Melanie van der Horst, the Amsterdam city official who introduced the ban."A few years ago, we only got around 20 complaints about fatbikes. Now we have more than 2,000," she told AFP in an interview in the park.Aside from the nuisance value, there is a safety aspect, given the fatbikes' popularity among children, added the official.Fatbikes are supposed to have a maximum speed of around 25 kph, but they are often illegally souped up to reach anywhere between 50 and 60 kph."Imagine an 11-year-old child driving around town at 50 kph on a big, souped-up fatbike. It's extremely dangerous," said van der Horst.Children have been rushed to hospital with serious injuries after fatbike accidents, she said, including brain injuries and torn knee ligaments."Doctors say it is the same level of impact as a motorcycle accident."'Goes very fast'