. It seems that electric brakes are legal, to my surprise, but need to be modified at minimum:
Differences between American caravans and trailers, and European regulations
1 Operating brakes
It is common on American caravans/trailers with electric brakes to have an electrical device
mounted in the towing vehicle which the driver operates manually to apply the brakes of the trailer
independent to the brakes on the tow vehicle. This is prohibited in Europe where the regulations
demand that the service braking system must be applied without the driver removing his hands
from the steering control.
2 Mounting sensor devices
Alternatively, American caravans/trailers with electric brakes can have an electrical device mounted
in the towing vehicle which senses deceleration in the towing vehicle and transmits a signal to the
caravan/trailer braking system to operate the brakes. European requirements demand that this type
of device must be mounted on the caravan/trailer.
3 Supply of electricity for electrical braking systems
The electrical energy required for the electrical braking system must be supplied to the trailer by
the towing vehicle. If there is a battery on the trailer which is fed by the power supply unit of the
towing vehicle, the power from the battery must be disconnected during application of the service
4 Time delays
Some American caravans/trailers rely on a signal from the towing vehicle stop lamps to initiate
braking on the caravans/trailers. Owners of such vehicles need to be aware that the system may
not meet the requirement for brake response time. European regulations demand that the time
In the case of a semitrailer or centreaxle trailer, the maximum mass to be considered for classifying the trailer
corresponds to the static vertical load transmitted to the ground by the axle or axles of the semitrailer or centreaxle trailer when coupled to the towing vehicle and carrying its maximum load.
delay between the time at which the driver applies the brakes and the time at which the braking
force on the least favourably placed axle reaches the level corresponding to the prescribed brake
performance must not exceed 0.6 seconds. This could be difficult to achieve on systems that have
to wait for the stop lamps to operate before the electronic control unit is activated and the system
produces the prescribed brake level.
5 Parking brakes
American caravans/trailers do not always have a parking brake. European requirements demand
that a caravan/trailer must be fittedwith a parking brake that is capable of holding the vehicle
stationary on an 18 per cent up or down gradient. Also, the working parts must be held in the
locked position by a purely mechanical device.
6 Braking mechanisms
American caravans/trailers do not always have brakes on all wheels, and it is common for a two axle
trailer to have brakes on only one axle. This is prohibited in Europe where regulations demand that
each individual wheel must brake.
Caravans and trailers fitted with a braking system are required to be stopped automatically if the
coupling separates while the trailer is in motion.
7 Inertia coupling
An inertia braking system must allow the trailer to be reversed with the towing vehicle without
imposing a sustained drag force exceeding 8% of the technically permissible maximum mass of the
trailer. Devices used for this purpose must act automatically and disengage automatically when the
trailer moves forward.
American “5thwheel” type caravans are considered semi trailers and, as such cannot use an
inertia (overrun) type braking system. The operation of the towing vehicle’s braking system must
directly operate the brakes on the trailer and electrically controlled systems are permitted.
8 Coupling(ball hitch) dimensions
The American ball hitch diameter is are usually 2 inches whereas the European (UK) is 50mm,
therefore the trailer coupling may need changing to be compatible with the 50mm ball.
9 UK Legislation
&U regulations demandcompliance with the technical requirements of Directive 71/320/EEC
including amendments up to and including Directive 98/12/EC. C&U Regulation 15 also recognises
the technical requirements of United Nations ECE Regulation 13 up to and including the 09 series
If the towing vehicle has a permissible gross weight in excess of 3.5 tonnes the maximum width and
length of thedrawbartrailer are 2.55 metres and 12 metres respectively. If however the gross weight of
the towing vehicle is 3.5 tonnes or less, then the maximum permissible width and length for a drawbar
trailer are 2.55 metres and 7 metres respectively. In both cases, the overall length of the towing vehicle
and trailer must not exceed either 18m or 18.75m depending on the type of towing vehicle.
If the vehicle combination (not including buses) is of the articulated category, regardless of the gross
weight of the towing vehicle,the maximum permissible width and length of the semitrailer are 2.55
metres and 12.2 metres respectively. The overall length of the towing vehicle and trailer must not exceed
The C&U definition of the overall length of a trailer makes it clear that the coupling device and
drawbar are not included in the length dimension. In the case of a caravan, where a protective box
is mounted on to the front(for example to hold gas storage tanks)andis supported on the draw
bar, this box is included in the overall length.
The above information relates to basic construction requirements and some aspects of the use of
trailers. In addition it is recommended that you check whether you have the appropriate Driving
Licence entitlement and whether the vehicle or combination of vehicles requires a tachograph to
record driver’s hours. The latter will apply to most vehicles and combinations of vehicles above
3500kg gross weight, where used for commercial purposes.
For Driving Licence enquiries contact:
DVLA Customer Enquiries, Telephone0300 790 6801
Further details are available at: https://www.gov.uk/