A mobility scooter is an electrically-powered scooter for those with mobility problems.
UK law divides mobility scooters (along with powered wheelchairs) into two categories - Class 2, and Class 3, invalid carriages.
Class 2 carriages have a maximum speed of 4mph, and cannot be used on the road (except where there is no footpath). They do not require registration.
Class 3 carriages have a maximum speed of 8mph, and can be used the road - but have a maximum speed of 4mph off the road. Class 3 carriages require registration, and cannot be used by those under 14.
Class 3 carriages also cannot be used in bus lanes, or cycle lanes.
Mobility scooters and powered wheelchairs cannot be used on cycle paths marked 'cycles only'.
This differs from the situation in the Netherlands, where mobility scooters and powered wheelchairs are free to use cycling infrastructure.