The Siemens Datatrak Automatic Vehicle Location System (AVLS) has been in operation for almost two decades. It provides a unique, reliable, and secure vehicle tracking solution for security applications such as cash-in-transit vehicles. There are several parts to an A VLS, one of which is the navigation system that actually determines the location of a vehicle. Datatrak have developed and operate a navigation system based on a network of low powered, low frequency (LF), transmitters around the area of interest. It also provides the timing requirements for the whole system. Designing a new network is fraught with complex issues that need to be resolved to ensure optimum use is made of the design. Until recently, most of the design work to establish the coverage and performance of the network had been made by manual means, using the vast experience of engineers and rules-of-thumb as guidance. This costs time and money. This research reviews the methods used by the engineers with a view to improving them using computer modelling techniques. Some of the coverage and performance factors have already been computer-modelled in recent research studies. These principles have, for the first time, been applied to the Datatrak system. However, the results of this research go further than those of computer models of other LF navigation systems. The amount of uncertainty in the position fix can now be predicted using novel techniques. Further, Datatrak engineers have never been able to predict accurately the actual propagation delays between transmitters and receivers. This shortcoming has been overcome by applying to Datatrak novel techniques recently developed for predicting Loran-C Additional Secondary Factors (ASFs). The model has then been further developed to predict for the first time the absolute accuracy of the positions, plus the ' confidence factor', a measure of how well multiple measurements align. This unique model will enable Datatrak engineers to see which areas need more attention. All this can be done before the first mast has been erected. The final implementation of the model is a Windows-based software suite that will enable Datatrak engineer to control the model easily and apply different scenarios.