Abstract: A fleet management system for monitoring the tread depth of a plurality of tyres in use in a fleet of vehicles, includes an electronic database of information relevant to the depth of tread for each of a plurality of tyres in use in a fleet of vehicles, an apparatus (100) for testing vehicle tyres, the apparatus (100) including eddy current sensors (120) arranged for detecting the relative position of a metallic reference point within a tyre, and an electronic controller for automatically updating said electronic database in response to test data received from said apparatus (100).