Dutch authorities seized 16,500 ‘fat bikes’ that were imported from China - with the Human Environment and Transport Inspectorate (ILT) reporting that they were actually illegal mopeds.

The NL Times reports the shipment was halted in Rotterdam, while another 1,000 unapproved models were found in a Dutch distribution centre. The seizure is part of an investigation the ILT has been conducting since July.

The legal motor power assistance limit for e-bikes in the Netherlands is 25km/h (15.5mph), but there is a growing concern about so-called 'fat bikes' as many do not comply.

Dutch police have been using roller test benches to check the maximum speed of e-bikes and mopeds across the Netherlands. As well as failing to comply with speed restrictions, some models also have a motor of more than the maximum allowed 250W or a throttle that allows riders to go faster than 6km/h (3.7mph) without pedalling.

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According to the ILT, manufacturers, importers and sellers must ensure vehicles comply with legal regulations before they are sold.

“You can’t expect young people and their parents to see the difference between a regular e-bike and an illegal one," said a spokesperson. "It is up to the industry to prevent them from buying a cheating e-bike.”

Referencing the seizures, the ILT said: “An unapproved moped does not suddenly meet the legal requirements of an electric bicycle with a simple push of a button or software update. Fatbikes that go too fast often already have an engine that is too powerful and other technical features of a moped.”

The inspectorate also said they see a growing number of cheaper, unsafe and unapproved mopeds on offer in the Netherlands. “It is [important] that these illegal mopeds disappear from our streets as quickly as possible. And that starts by putting a stop to their sale via official trade channels.”