In the industry of over-the-road trucking, particularly in the employment of a semitrailer, also known as a semi-tractor trailer, comprising a tractor and a trailer, there has long existed the problem of meeting the weight specifications of the vehicle and its load required by highway authorities. A maximum load weight is set for the entire rig and also separate maximum weight limits are set for each axle. Therefore, care must be taken, not always observed, to ensure that the load is evenly placed within the trailer so as not to exceed the weight limit over any one axle.
In many situations, the driver may pick up a trailer on his rig without having knowledge of the weight of the load or how it is distributed in the trailer. In those instances, the driver must have access to a scale and weigh not only the total load, but also each separate axle to determine whether or not he meets the load weight specifications. For instance, a maximum permissible axle load may, for example, be 12,000 lbs. on the front axle, 34,000 lbs. on the two rear axles of the tractor and 34,000 lbs. for the two rear wheels of the trailer totalling 80,000 lbs. on an eighteen wheeler truck. A problem arises where the trailer is unevenly loaded and the major portion of the load is at the front or the rear of the trailer which would increase the weight on the two rear axles of the cab to exceed or be less than the 34,000 lbs. limit even though the total axle scale weight of the rig may be under 80,000 lbs.
The fifth wheel assembly on the tractor of the semitrailer is conventionally adjustable forwards or backwards to distribute the weight load over the axles. Similarly, the rear of the trailer is adjustable to adjust the axle back and forth to take the weight off the fifth wheel where the load is at the front or to move the axles to the rear for a heavy rear load. When the driver does not know the distribution of the load in the trailer, he must adjust the axles by trial and error. The axles must be weighed on the scales each time after an adjustment to determine the new load distribution. This presents an undesirable situation in that much time and effort are expended. There has been a long felt need in the trucking industry to develop means for readily determining the load distribution on a trailer without requiring the inefficient method of continuously driving on weight scales after each adjustment.