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The use of longer articulated vehicles, up from 15.5 to 16.5m, became legal in the spring. CM looks at how legislation has affected trailer operations over the years.
• EC directive 89/461, back in the spring, allowed the use of longer articulated vehicles, up from 15.5 to 16.5m, and was incorporated into British Construction and Use Regulations (SL 1990/317).
It provides for the use of 2.5m wide semi-trailers which can be as much as 13.61m long but they have to meet specific turning requirements. There is a general rule for all articulated combinations longer than 15.5m to conform to turning circle directive 85/3/EEC which states the vehicle must be able to negotiate within a corridor determined by a 12.5m outer radius and a 5.3m inner radius.
For those operators interested in calculating turning circles arithmetically for artic combinations above 15.5m, CM has produced a diagram and formula which is available on request.
CLEARANCE
At first, the king pin position was set at 12m from the rear of the trailer and a swing clearance of 2.4m was required. However, to allow older tractors to be used with the new trailer equipment, an amendment (SL1990/1163) was introduced to allow a second pin position which would give a shorter front overhang.
A special case was also made for the car transporter semi-trailer and the pin position was revised to 1.2.5m from the rear.
CRITERIA
Tractor/trailer matching criteria ISO 1726 (partly embodied in the legislation) requires a minimum clearance of 80mm between the back of the cab and the front of the trailer, canted at an angle of 60, at a height of 250mm above the fifth wheel. The maximum distance between the front bumper and the pin position is restricted to 4.5m.
Where the laden weight of an articulated vehicle exceeds 32.52 tonnes then the height is limited to 4.2m and where the travelling height is more than 3.66m the actual height (in feet and inches) must be stated inside the cab.
A demountable body and ship's container are deemed part of the vehicle in transit. Drawbar trailers do not usually exceed 7m in length.
EC directive 85/3 originally provided for a common upper European limit of 40 tonnes for five and six-axled drawbar and articulated vehicles from 1 July 1986. Both UK and Eire governments sought derogation to limit maximum weight for articulated vehicles to 38 tonnes, and drawbars to just 32.52 tonnes, until 31 December 1998. However, weight constraints on four-wded articulated and drawbar vehicles are likely to be relaxed from the beginning of 1993. Provision already exists to allow a gross weight of 18 tonnes for a twoaxled drawbar trailer so we could be faced with the anomaly of a 35 tonne drawbar
combination on four axles and a lower weight restriction on five axles.
REGULATIONS
Sideguards must be fitted to semi-trailers manufactured after May 1983 which have a plated train weight of more than 32.52 tonnes or over 26 tonnes if the distance between king pin and the leading trailer axle exceeds 4.5m. Drawbar trailers exceeding 1.02 tonnes, also manufactured after May 1983, and with a wheelbase of more than 3m, must also be equipped with sideguards. There are, however, certain exemptions including agricultural and tipping trailers as well as trailers built to carry timber, beams or girders. In most cases maximum permitted weight is dependent on the number of axles and their spread. Sideguard regulations were introduced to give added protection to cyclists and pedestrians and was part of the price industry had to pay for 38tonners. But by linking the rule to the heavier vehicles, those most likely to be used in urban areas were missed out.
The regulations are specific on the area which must be protected "so far as it is practicable". To summarise, none of the vertical or horizontal surfaces, in a plane adjacent to the side of the vehicle, must measure less than 100mm nor any vertical gap be more than 300mm and all external edges must have a radius of at least 2.5mm. The structure has to be strong enough to withstand a force of 21(..N applied square on without deflecting more than 150m, or only 30mm if less than 250mm from the rearmost part.
A rear underrun bumper is also a requirement for trailers which were built after May 1983, if they weigh more than 1.02 tonnes.
EC directive 221/1970 and 490/1979 are again specific but in general apply only to the chassis manufacturer. Areas most likely to concern operators are those which permit modifications to fit tail-lifts and demountable bodies.
STANDARDS
Spray suppression is another area which affects trailers.
All trailers over 3.5 tonnes built after I May 1985 and all already in service over 16 tonnes gross weight with two or more axles have to be equipped by one or other of the commercially available systems which meet the requirements of BSAU200. The British Standard (part 1 and 2) includes all dimensional requirements. To make them less prone to being damaged in some types of operation, the ground clearance was increased in a 1987 amendment from 150 to 200mm and 300min for tractor drive axles if used on RO-RO ferry operations.
All trailers over 3.5 tonnes constructed after 1 January 1968 must have brakes which operate on all wheels to efficiency levels that are equal to those of the draw
ing vehicle. The minimum service requirement is 0.5g. Secondary brakes need only operate on a minimum 50% of the wheels and give an overall performance of just 0.25g, while a parking brake must be able to hold the trailer stationary on a gradient of at least 16% (1:6.25). In line with EC directive 88/194, British C & U regulations have been changed so that trailers over 10 tonnes gross weight, manufactured on or after 1 October 1991 must have anti-lock brakes.
OFor a definitive guide to commercial vehicle legislation we recommend Kitchins Road Transport Law, edited by Jim Duckworth of CM's sister publication Motor Trasport. For more details phone: 081-661 3713.
0 by Bill Brock