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It is common practice for countries to have general access “workhorse” vehicles which are subject to one set of limits and limited access vehicles subject to a different and higher set of limits. The first option for improving productivity is usually a simple combination representing economies of scale using existing trailer units. An alternative to this practice, already being adopted in most countries, is the use of innovative vehicles. As part of nations' size and weight systems, processes for reviewing and changing limits are becoming more selective and are using elements of performance-basing. There is persuasive evidence from a number of countries that current size and weight systems are extremely effective for the simple considerations of vehicle width and height, and for pavement wear. A misplaced emphasis is placed on overall length in some countries and low-speed offtracking is a well-recognized, but very poorly controlled, performance measure.

The U.S. Department of Transportation's Comprehensive TS&W Study addressed the safety impacts of potential changes to TS&W limits from two perspectives: (1) the assessment of crash information and exposure data (vehicle miles traveled), and (2) the evaluation of stability and control performance of several truck configurations in terms of static roll stability, rearward amplification, and load transfer ratio. This paper addresses the analytical approach used to evaluate safety impacts from the latter perspective. The vehicle performance measures were estimated using simulation models. Several vehicle parameters were varied in a large parametric analysis for use in the study.

A major co-operative international research program known as DIVINE (Dynamic Interaction between Vehicles and Infrastructure Experiment) has been completed by the Organisation for Economic Cooperation and Development OECD). DIVINE involved seventeen OECD member countries, and included specialists in vehicles, pavements, bridges, road management and transport policy. Inter-linked research projects were carried out in nine countries and the project took almost four years to complete. DIVINE set out to investigate the benefits of “road-friendly” suspensions for reducing pavement wear and to develop better means of assessing vehicle suspensions for road-friendliness. This paper summarises the most important results of DIVINE and presents means of assessing and simulating the road-friendliness of truck suspensions. Dynamic loading depends on the vehicle suspension, and the use of air suspension generally reduces dynamic loading.