In many countries road traffic is growing rapidly in volume and in the size and weight of the vehicles using the roads. As a consequence, highway engineers concerned with designing new roads or the strengthening of existing roads require reliable information about the distribution of axle loads for existing traffic as well as information on national or regional axle load trends. This information is required so that accurate forecasts can be made of the axle loads that a road will have to carry over it’s design life. The importance of reliable traffic information for pavement design purposes is emphasised by the widely accepted engineering law that the degree of pavement damage caused by an axle load is proportional to approximately the fourth power of the axle load. This implies that the heaviest ten percent of axle loads can often cause more pavement damage than the rest of the traffic combined. To provide adequate information on axle load distributions, road-side surveys of axle loads are required. Such surveys can conveniently be made using portable wheel or axle weighing devices that are widely available. This note describes the methodology and procedures required to carry out both a traffic count and an axle load survey and includes methods of data analysis for pavement design purposes. The procedures are based on tried and tested methods used by experienced staff who have undertaken numerous axle load surveys world-wide.
Transport Research Laboratory (2004) A guide to axle load surveys and traffic counts for determining traffic loading on pavements. Transport Research Laboratory (TRL) Overseas Road note 40
ORN40 A guide to axle load surveys and traffic counts for determining traffic loading on pavements
Published 1 December 2004