Aye with Air brakes that auto engage if you lose the trailer unit?
Here it's been posted a few time but here it is again. There seems to always be something they can get you on if you use one.
When an "A" frame is attached to a vehicle (e.g. a motor car) and towed by a motor vehicle (e.g. motorhome) we believe the "A" frame and car become a single unit and as such are classified in legislation as a trailer. As a consequence the car and A-frame are required to meet the technical requirements for trailers when used on the road in Great Britain. These requirements are contained within the Road Vehicles (Construction and Use) Regulations 1986 (SI 1986/1078) as amended (C&U) and the Road Vehicles Lighting Regulations 1989 (SI 1989/1796) as amended (RVLR).
Trailers having a combined axle mass not exceeding 750kg are not required to have brakes fitted. However, if the trailer (regardless of mass) is fitted with a braking system, then all brakes in that system must operate correctly. The regulations do not include design constraints on how this should be achieved but, for example, it could be met by direct linking of the trailer brakes to the brake system of the towing vehicle or by automatic inertia (overrun) operation via the towing hitch. Inertia systems can only be used for trailers with a maximum combined axle mass of 3500kg.
Regulations 15 and 16 set out the braking requirements - including minimum braking efficiencies for trailer brakes. Subject to certain age exemptions, the regulation requires the braking system to comply with the construction, fitting and performance requirements of European Community Directive 71/320/EEC along with its various amending Directives. The most recent consolidated directive is 98/12/EC. Alternatively the braking system can comply with the corresponding UNECE Regulation No.13.09.
In addition, C&U Regulation 18 requires the braking system to be maintained in good and efficient working order. If the brakes of the towing vehicle do not directly operate the trailer brakes the use of an inertia (overrun) system is acceptable. If the trailer braking system has power assistance (i.e. servo or full power) it is likely that this assistance will be required while in motion to meet the required braking efficiencies. This is because once the vacuum reservoir is depleted it is possible that the brakes will not meet the braking efficiency. To prevent the trailer being used illegally a remote vacuum pump, powered from the tow vehicle, could be installed to recharge the reservoir, alternatively a source could be made available from the tow vehicle. From 1 October 1988 the inertia braking system was required to allow the trailer to be reversed by the towing vehicle without imposing a sustained drag and such devices used for this purpose must engage and disengage automatically. This will be very difficult to achieve on an "A" frame using an inertia (overrun) device.
Other provisions from Regulation 15 and Regulation 86A of C&U require the fitting and use of a secondary coupling system in which the trailer is stopped automatically if the main coupling separates whilst the combination is in motion. Alternatively, in the case of trailers up to a maximum mass of 1500kg, the drawbar must be prevented from touching the ground and the trailer able to retain some residual steering.
Whilst being towed, trailers are subject to the relevant requirements given in RVLR, including the use of triangular red reflectors. There would be further requirements for the display of the appropriate number plate, etc.
The use of "dollies" is intended for the recovery of broken down vehicles, not for the transportation of a vehicle from "A" to "B". Under Regulation 83 of C&U a motor car is permitted to tow two trailers when one of them is a towing implement and the other is secured to and either rests on or is suspended from the implement. Therefore as a trailer if the maximum laden weight of the dolly exceeds 750 kg it must be fitted with operational brakes, additionally the brakes on the wheels of the second trailer (the towed car) must work and meet the specified requirements. Again this would be very difficult for the rear brakes of a motor car, on their own, to meet the 50% braking efficiency required for a trailer. The dolly would also be required by Regulation 22 of C&U to be fitted with suspension. Regulations 19 and 22 in C&U permit a broken down vehicle to be recovered without complying with these requirements. However, there is further legislation under the Road Traffic Act that introduces a limitation on the maximum speed that the combination can be driven; this is 40mph on motorways and 20mph on other roads.
