A machine (100, 200) of a kind comprising a body (130, 230, 330) and an implement (120, 220, 320), the machine comprising a system configured to define a safety zone in the vicinity of the implement (120, 220, 320), the system comprising: a processor configured to receive a plurality of system inputs and to deliver a system output comprising criteria that define a position and one or more dimensions of the safety zone; and wherein the plurality of system inputs comprises: (a) first system input data relating to a type and/or a dimension of the implement; (b) second system input data relating to a current position of the implement; (c) third system input data relating to user input control of a first type that governs ground propulsion of the machine; and (d) fourth system input data relating to user input control of a second type that governs movement of the implement relative to the body and operation of the implement; wherein the processor is configured to process the plurality of system inputs in order to determine the system output, wherein the system output represents guidance in relation to a future trajectory of the safety zone, wherein the future trajectory is calculated based on current system input data; characterized in that, the machine further comprising a data library including data corresponding to values for each of the first, second and third system input data and, for each combination of input data values, a corresponding output data value, wherein the step of processing the plurality of inputs in order to determine the system output comprises searching the data library for an output data value that corresponds with the first, second and third system input data values. a processor configured to receive a plurality of system inputs and to deliver a system output comprising criteria that define a position and one or more dimensions of the safety zone; and wherein the plurality of system inputs comprises: (a) first system input data relating to a type and/or a dimension of the implement; (b) second system input data relating to a current position of the implement; (c) third system input data relating to user input control of a first type that governs ground propulsion of the machine; and (d) fourth system input data relating to user input control of a second type that governs movement of the implement relative to the body and operation of the implement; (a) first system input data relating to a type and/or a dimension of the implement; (b) second system input data relating to a current position of the implement; (c) third system input data relating to user input control of a first type that governs ground propulsion of the machine; and (d) fourth system input data relating to user input control of a second type that governs movement of the implement relative to the body and operation of the implement; wherein the processor is configured to process the plurality of system inputs in order to determine the system output, wherein the system output represents guidance in relation to a future trajectory of the safety zone, wherein the future trajectory is calculated based on current system input data; characterized in that, the machine further comprising a data library including data corresponding to values for each of the first, second and third system input data and, for each combination of input data values, a corresponding output data value, wherein the step of processing the plurality of inputs in order to determine the system output comprises searching the data library for an output data value that corresponds with the first, second and third system input data values.