sentences:  In Europe, manufacturers tend to send some of their products to another company (owned by the parent) to be converted into a special heavy duty version.Most heavy haulage and heavy lift engineering firms employ heavy duty tractor-unit models that can accommodate a ballast box.Countries where modernisation is taking place, such as regions of the Middle East and South Africa, operate larger number of ballast tractors due to the greater frequency of heavy loads (such as power station components).