Driving and operating 125The permitted trailer load applies upto the specified incline and up to analtitude of 1000 metres above sealevel. Since engine power decreasesas altitude increases due to the airbecoming thinner, therefore reducingclimbing ability, the permissible grosstrain weight also decreases by 10 %for every 1000 metres of additionalaltitude. The gross train weight doesnot have to be reduced when drivingon roads with slight inclines (less than8 %, e.g. motorways).The permissible gross train weightmust not be exceeded. This weight isspecified on the identification plate3 165.Vertical coupling loadThe vertical coupling load is the loadexerted by the trailer on the couplingball. It can be varied by changing theweight distribution when loading thetrailer.The maximum permissible verticalcoupling load is specified on thetowing equipment identification plateand in the vehicle documents. Alwaysaim for the maximum load, especiallyin the case of heavy trailers. Thevertical coupling load should neverfall below 25 kg.In the case of trailer loads of1200 kg or more, the vertical couplingload should not be less than 50 kg.Rear axle loadWhen the trailer is coupled and thetowing vehicle fully loaded (includingall occupants), the permissible rearaxle load (see identification plate orvehicle documents) must not beexceeded.Towing equipmentCautionWhen operating without a trailer,remove the coupling ball bar.Towing equipment audiblewarningFor vehicles fitted with towingequipment, when connected to atrailer the pitch of the audible warningchanges upon operation of the turnsignals.The pitch of the audible warning willchange if a turn signal light on thetrailer or the towing vehicle fails.
