A homemade motorcycle stopped on the M25 was described by a traffic officer as the "most unusual vehicle" he had apprehended in 26 years.
It was spotted just before junction 21 for the M1 in Hertfordshire at about 20:30 BST on Sunday.
A police spokeswoman said the vehicle was approved and registered by the DVLA.
Another roads policing officer called the vehicle a "homemade electric motorcycle" which was "made from bits of balsa wood and duct tape".
Sgt Stephen Andrews, from the Bedfordshire, Cambridgeshire and Hertfordshire Roads Policing Unit, said: "This is certainly not a vehicle that is seen very often on our roads but after road side inspection we couldn't find anything that would prevent the rider to continue his journey.
A spokeswoman for the force said the vehicle was "registered as a motorbike with a 'shell' around it made mostly out of fibreglass and plastic".