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Road Safety (Vehicles) Regulations 2021
Part 6Vehicle configuration and dimensions
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Part 6—Vehicle configuration and dimensions
This Part sets out various requirements covering the suspension on vehicles and size limits for single vehicles and combinations of vehicles, so that they can be operated safely with other traffic, without taking up too much road space or damaging the road and structures on the road.
Generally, the limits in this Part apply to a vehicle and any load it may be carrying. Specific requirements for loaded vehicles are covered by other laws.
Division 1—Axles
58 Axle configuration
(1) A motor vehicle must have only—
(a) one axle group, or single axle, towards the front of the vehicle; and
(b) one axle group, or single axle, towards the rear of the vehicle.
(2) A trailer must have only—
(a) one axle group or single axle; or
(b) 2 axle groups, 2 single axles, or one axle group and single axle, in the following configuration—
(i) one axle group, or single axle, towards the front of the vehicle, with all the wheels on the axle group or single axle connected to the steering mechanism for that part of the trailer;
(ii) one axle group, or single axle, towards the rear of the vehicle.
(3) A semi-trailer that is extendible, or is fitted with sliding axles, must—
(a) have a securing device that—
(i) can securely fix the extendible part or sliding axles to the rest of the vehicle in any position of adjustment provided; and
(ii) is located in a position that can prevent accidental or inadvertent release, if the device is mounted on the chassis of the vehicle; and
(iii) is fitted with a visible or audible warning system to indicate to a person standing beside the vehicle that the device is not engaged; and
(iv) is fitted with a way of preventing loss of air from the air brake supply, if the device uses air from the brake system and fails in a way allowing air to escape; and
(v) is held in the applied position by direct mechanical action without the intervention of an electric, hydraulic or pneumatic device; and
(b) be built so the adjustable parts of the vehicle remain connected if the securing device fails.
59 Retractable axles
***retractable axle*** means an axle with a means of adjustment enabling the axle to be raised or lowered relative to the other axles in the axle group.
(2) For the Vehicle Standards, a retractable axle is taken to be an axle only when the retractable axle is in the lowered position.
Division 2—Dimension requirements
60 Meaning of rear overhang and rear overhang line
(1) The rear overhang of a vehicle is the distance between the rear of the vehicle and the rear overhang line of the vehicle.
(2) For a vehicle with an axle group at the rear consisting of only one axle, the rear overhang line is a line running along the centre line of the axle.
(3) For a vehicle with an axle group at the rear consisting of 2 axles, one of which is fitted with twice the number of tyres as the other, the rear overhang line is a line running parallel to the axles that is—
(a) closer to the axle carrying the greater number of tyres than the line is to the other axle; and
(b) located at one-third of the distance between the 2 axles.
(4) For a vehicle with an axle group at the rear that is not an axle group mentioned in subclause (2) or (3), the rear overhang line is a line running parallel to the axles down the centre of the axle group.
(5) For the purposes of applying subclause (2), (3) or (4) to a vehicle, if an axle group includes at least one steerable axle, that axle is to be disregarded unless—
(a) the group consists of only one axle and that axle is a steerable axle; or
(b) all the axles in the group are steerable axles.
Figure 9: Illustration of rear overhang and rear overhang line—motor vehicle.
Figure 10: Illustration of rear overhang and rear overhang line—vehicle with tri-axle group at rear.
Figure 11: Illustration of rear overhang and rear overhang line—semi-trailer.
61 Length of single motor vehicles
The maximum length for a motor vehicle is specified in regulation 205 or in Schedule 6.
62 Length of single trailers
The maximum length for a trailer is specified in regulation 206 or in Schedule 6.
63 Length of combinations
The maximum length for combinations is specified in regulation 207 or in Schedule 6.
64 Rear overhang
The requirements in respect of the rear overhang of vehicles are specified in regulation 208 or in Schedule 6.
65 Length of trailer drawbars
The requirements in respect of the length of trailer drawbars are specified in regulation 209.
66 Width
The maximum width for a vehicle is specified in regulation 204 or in Schedule 6.
67 Height
The maximum height for vehicles is specified in regulation 203 or in Schedule 6.
68 Ground clearance
The requirements for the ground clearance of vehicles are specified in regulation 210.
Part 7—Lights and reflectors
This Part deals with how the lights on a vehicle must be fitted and work so that the driver can see the road, pedestrians and other vehicles at night, and can signal to others.
Other laws provide for when certain lights must be switched on.
In this Part, the description "yellow" is used as a more modern term, instead of the description "amber" which is used in earlier legislation and some ADRs.
Division 1—Application of particular requirements
69 Part does not apply to particular vehicles
(1) This Part does not apply to a vehicle built before 1931 that is used only in the daylight.
(2) This Part does not apply to a vehicle built before 1946 that is used mainly for exhibition purposes.
70 Particular requirements apply only at night
The requirements of this Part for a light, except a brake or direction indicator light, to be visible over a stated distance apply only at night.
Division 2—General requirements for lights