There are such things as road-legal quad bikes. They are classed as quadricycles and fall into the same licensing group as motorcycles, namely B1.
Any powered vehicle used on the public highway must comply with all aspects of road traffic law. For example, it must:
� Have European Community Whole Vehicle Type Approval (or motorcycle Single Vehicle Approval)
� Be registered with the Driver and Vehicle Licensing agency (DVLA)
� Be road-taxed
� Be insured
� Comply with the Road Vehicles (Construction & Use) Regulations 1986 as amended and the Road Vehicles Lighting Regulations 1989 as amended.
� Riders must be 16 or over and must hold a valid driving licence with group B1 entitlement.
The only powered vehicles to which these requirements do not apply are electrically-assisted pedal cycles (as defined by regulations) or powered wheelchairs and powered scooters designed for disabled people (known as "invalid carriages" in law). Only "invalid carriages" may be used on the pavement beside the road.
Current UK law only specifies compulsory use of helmets with motor bicycles; not trikes nor quads.