They are without question illegal for use in any area the public has access to.
The fundamental in UK law is that all motorised vehicles are illegal unless specifically allowed in a law. There is no law allowing these powered scooters and the DfT has on more than one occasion said they are illegal for use.
Here is a complete list of exemptions from being type approved as motor vehicles. N.B. Exemption (c) does not apply since it has been ruled in a test case that the user is not a pedestrian:
2. This Regulation does not apply to the following vehicles:
(a) vehicles with a maximum design speed not exceeding 6 km/h;
(b) vehicles exclusively intended for use by the physically handicapped;
(c) vehicles exclusively intended for pedestrian control;
d) vehicles exclusively intended for use in competition;
(e) vehicles designed and constructed for use by the armed services, civil defence, fire services, forces responsible for maintaining public order and emergency medical services;
(f) agricultural or forestry vehicles subject to Regulation (EU) No 167/2013 of the European Parliament and of the Council of 5 February 2013 on the approval and market surveillance of agricultural and forestry vehicles ( 1 ), machines subject to Directive 97/68/EC of the European Parliament and of the Council of 16 December 1997 on the approximation of the laws of the Member States relating to measures against the emission of gaseous and particulate pollutants from internal combustion engines to be installed in non-road mobile machinery ( 2 ) and Directive 2006/42/EC of the European Parliament and of the Council of 17 May 2006 on machinery ( 3 ) and motor vehicles subject to Directive 2007/46/EC;
(g) vehicles primarily intended for off-road use and designed to travel on unpaved surfaces;
(h) pedal cycles with pedal assistance which are equipped with an auxiliary electric motor having a maximum continuous rated power of less than or equal to 250 W, where the output of the motor is cut off when the cyclist stops pedalling and is otherwise progressively reduced and finally cut off before the vehicle speed reaches 25 km/h;
(i) self-balancing vehicles;
(j) vehicles not equipped with at least one seating position;
(k) vehicles equipped with any seating position of the driver or rider having an R-point height ≤ 540 mm in case of categories L1e, L3e and L4e or categories L2e, L5e, L6e and L7e.
Also note that exemption still does not legalise use, each classification needs a specific law describing and permitting use. For examples, (i) exempts self-balancers like the Segway from being a motor vehicle, as does (j) for motorised scooters, but there is no law permitting their use so they are illegal in most circumstances.
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