A study was undertaken to quantify the magnitude of the pavement damage done by overweight trucks in New Jersey. This was accomplished using the AASHTO 18-kip equivalent axle load parameter, established engineering-economic procedures, and data obtained from the New Jersey State Police. Questions specifically addressed include (a) How much pavement damage is attributable to overweight trucks?(bl What are the costs associated with this damage?(c) Are these costs adequately covered by the revenues collected from the overweight violators?(d) Is mandatory off-loading (requiring violators to immediately lighten their loads at the ticketed location) justifiable? It was found that detected overweight trucks cause a relatively small shortening of pavement life and, had they been successfully offloaded, a negligible savings would have resulted. However, there is serious concern that the number of overweight trucks actually detected represents only a small fraction of the total number of overweight violators. Attempts to estimate the total overweight truck population suggest that the total pavement damage attributable to all overweight trucks may approach $20 million per year. It was therefore concluded that a substantial increase in the revenue generated by overweight trucks may be appropriate.

The consequences of operating overweight trucks are a timely concern, particularly in light of the Surface Transportation Assistance Act (STAA) of 1982 that standardized truck size and weight restrictions across the nation. This analysis, requested by the Office of the Attorney General of New Jersey, specifically addresses the engineering and economic implications of excessive pavement loading in a state where maximum weight limits already comply with the federally mandated standards Ill· Knowledge of these implications should provide guidance in making policy decisions pertinent to the mode and level of truck weight enforcement. This required that pavement damage be defined in terms of an established parameter and that the extent of this damage be quantified in a rational manner. It is common knowledge to highway engineers that pavement damage increases dramatically with increasing vehicle weights. A legal, fully loaded tractor trailer combination may cause approximately 10, 000 times the pavement damage caused by the heaviest of passenger cars. Intuitively, it might appear that illegally loaded trucks would cause substantially more damage than their legally loaded counterparts. However, this inference is only partly correct. Analysis of the comparative pavement damage resulting from the myriad possible vehicle loadings is conveniently accomplished with the AASHTO 18-kip (18,000-lb) equivalent axle load (EAL) parameter (~, pp. 162-167). This parameter was developed to provide a common basis against which to assess the effect of repetitive loads on pavement serviceability. It permits information on vehicle configuration and weight on each axle grouping to be transformed into a single fundamental parameter, expressed as multiples of the pavement damage done by the standard 18-kip single axle load used in pavement design. A 28-kip load on a tandem axle on a 9-in. rigid pavement, for example, will ordinarily cause only 85 percent of the damage that would be done were an 18-kip load on a single axle applied to the same