European type approval 94/20/EC
In the U.K, with effect from 1st August 1998 all Passenger Carrying Vehicles up to 3500kgs Gross Vehicle Weight (M1 Vehicles) can only be fitted with European Type Approved towbars if the vehicle has received European Whole Vehicle Type Approval.
Non M1 vehicles, light commercial vehicles and private imports from outside the EEC do not need Approved Towbars; however, most car and some Light Commercial Vehicles such as vans commonly use the Type Approved Towbar.
Most towbar manufacturers have allowed, in the towbar test and approval application, for the inclusion of various accessories, often by including a spacer in the towbar kit, which is removed when the accessory is fitted. This information should be clearly stated in the fitting instructions. If there is any doubt, you should contact the towbar manufacturer. This would apply to all accessories that move the towbar rearwards from the towbar.
Design, Testing and Certification
The towbar manufacturer requires the following vehicle data to design a towbar:
- Manufacturer's specified fixing points.
- Gross vehicle weight or mass (GVW or GVM)
- Gross Trailer Weight or Mass (GTW or GTM) that the model of vehicle can tow.
This information is included in the Vehicle's Handbook. From this data the towbar manufacturer constructs a test load, called D Value, which will be used to test the towbar. As well as providing the test load, the towbar manufacturer is obliged to include a D value in kn on the towbar identification plate.
The "D" value is calculated as follows:
(GVW x GTW ) / (GVW + GTW) x 9.81/1000 (gravity)= kn
Where GVW is Gross Vehicle Weight, and GTW Gross Trailer Weight.
The maximum D value for an M1 vehicle is 17.7kn that represents a GVW of 3500 kgs towing GTW of 3500kgs.
It is possible to design a towbar that fits the whole range of models of one particular vehicle. Because Towing Capacity is related to GVM then each model may have a different value for D. To prevent overload of the Towing Vehicle refer to the Vehicle Manufacturers' Handbook to confirm the GTW for your particular model.
Towing with Heavy Goods Vehicles
The snatch loads imparted to the tow hitch by a commercial vehicle tend to be much higher than those of passenger cars, especially with a GVW up to 180000 kgs. These snatch loads will impart severe strain on the Trailers drawbar which may eventually damage the drawbar. It is therefore recommended that when towing with a Commercial Vehicle a shock absorbing towbar is fitted.