 Sometimes, the marshaller indicates directions to the pilot by driving a "Follow-Me" car (usually a yellow van or pick-up truck with a checkerboard pattern) prior to disembarking and resuming signalling, though this is not an industry standard.At busier and better equipped airports, marshallers are replaced on some stands with a Visual Docking Guidance System (VDGS), of which there are many types.On aircraft carriers or helipads, marshallers give take-off and landing clearances to aircraft and helicopters, where the very limited space and time between take-offs and landings makes radio communications a difficult alternative.