Using a fleet of automated guided vehicles (AGV) is an increasingly popular option for a transportation system in semiconductor fabrication plants (fab), where AGVs can either serve as a supplement to the already existing transport system or as a first step towards the automation of transports. AGV systems have a high number of design choices, which need to be taken into consideration when planning and operating such systems in a fab. In addition, the combination of various AGV system characteristics has effects on the system performance that are difficult to predict. In this publication important aspects and dependencies are outlined regarding major AGV system characteristics like layout topologies and minor system characteristics like vehicle handling time or vehicle velocity.