Vehicle sharing across DOT numbers is the pattern where the same physical trucks rotate through multiple operating authorities — sometimes within the same month, sometimes simultaneously across different authorities. FreightWaves investigations have documented examples involving dozens of vehicles previously or simultaneously operated across multiple DOT numbers. The pattern is a red flag because (a) the carrier’s declared fleet size on its MCS-150 does not reflect operational reality, (b) the insurance policy follows the authority rather than the VIN, so a single physical truck can be covered by three different policies in a single month, and (c) the FMCSA carrier registry does not automatically connect the dots. When you vet a carrier and find a roadside inspection footprint significantly larger than its declared fleet, vehicle sharing is one of the most likely explanations.