SMMT Guide on Trailers > Maximum Trailer Dimensions
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Maximum Trailer Dimensions
Length (excluding the coupling and drawbar) for a four or more wheeled trailer. 7 meters or 12 meters if towed by a vehicle over 3500kg GVW.
Length of towing vehicle and trailer combined 18 meters.
Maximum overhang of load from rear of trailer 3.05 meters.
Marking of rear overhang:
Between 1 metre and 2 metres, ensure the end is clearly visible by attaching a piece of cloth or similar.
Between 2 metres and 3.05 metres, a marker board as defined in the regulations must be fitted and must be illuminated at night.
If the overhang exceeds 3.05 metres, the police must be notified before commencing the journey.
"Long Vehicle" marker plate
Not a legal requirement, though for longer combinations, particularly where the towing vehicle is over 7500kg gross weight, it is advisable to fit a plate in the interests of safety. Details can be found in the Road Vehicle Lighting Regulations, Schedule 18.
Width 2.3 meters or 2.55 metersfor a trailer towed by a vehicle over 3500kg GVW.
Loads must not project more than 305 mm either side of the trailer.
Loads over 2.9 metres in width are classed as abnormal loads, and the police must be notified before commencing a journey.
Height no limit stated.
Recommended maximum height 3m or 1.7 x wheel track.
