Special Order (SO) vehicles are the largest and heaviest vehicles permitted to move on the highway network and can have gross weights ranging from 150 to 550 tonnes. The aim of this project was to develop a number of model vehicles that replicate the loading produced by real SO vehicles. If standard loading models can be developed to cater for the effects of SO vehicles, then structures on identified heavy load routes can be designed or pre-assessed for these model vehicles. This should expedite the process of clearing movement requests for SO vehicles and may also reduce the number of structures requiring strengthening.
In order to develop the models, it was first necessary to collect information on the range of physical characteristics associated with real SO vehicles. This included factors such as gross vehicle weight, individual axle weights, the spacing between axles, and the dimensions of the vehicles. This report presents the findings of the data collection phase of the project. It provides a broad summary of the characteristics of SO vehicle movements during the period 2000 to 2005, and a more detailed review of SO vehicle characteristics in the years 2004 and 2005.

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