Abstract: An asset tracking system includes a central control station with an associated datastore for storing asset information. The stored information includes multiple unique identifiers, each identifier being associated with an asset tracking unit in the form of a mobile base station asset tracking unit or a beacon asset tracking unit. The two types of tracking unit are fitted to assets such as vehicles. The mobile base station asset tracking units include GPS modules and can determine their position, and can also communicate with the central control station. The beacon asset tracking units can communicate with the mobile base station asset tracking units via short range radio transmissions and their positions can thus be determined from the position of nearby mobile base station asset tracking units. The control station includes a communication module which can receive, over an existing communication network, location data messages from a mobile base station asset tracking unit fitted to a first asset.