Computer simulation modelling techniques are basic engineering tools to investigate and predict the performance and mobility of agricultural tractors. Analytical methodologies developed by researchers to simulate and evaluate the terrain-operator-agricultural vehicle system and its subsystems are described. The techniques are classified as models and methods describing the subsystem interactions and relationships and the overall tractor-soil-implement system. The subsystem models and methods include: soil mechanics) the soil-wheel interactions, the soil-track interactions, the vehicle mechanics relationships, the soil-implement interactions, and the power train and hitching relationships. These models and methods were developed by various researchers as a means to optimize the tractive performance of the tractor by parameter sensitivity analyses.