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. Vehicle stability performance is not controlled in any effective way at present, although high-cube, low freight density size and weight systems tend to produce more stable vehicles. While productivity is often talked about in size and weight systems, there is little evidence of any convergence on an optimum solution. Our nations' size and weight systems produce GVWs which vary significantly and cubic capacities which vary dramatically.