Within VDM, a distinction is made between four types of resources: technicians, spare parts, contractors and knowledge. One need to think only of cash flows freed up as a result of smarter management or savings on warehouses, logistical employees, insurance and the avoidance of obsolete and surplus spare parts. In practise, it often turns out that the value potential of smart management of spare parts by far exceeds the value potential of the other resources. As figure 1 shows, a natural tension exists between the four value drivers. That is why today's maintenance manager is continually searching for the right balance between these value drivers. It is important to know how they square up to each other. One can determine this instinctively but many corporate managers require a financial validation because, for example, it will be a decisive factor in investment decisions or because stakeholders (e.g. financial manager, production manager) are not prepared to accept a judgement based on instinct. This is a situation where one should use the VDM formula. Formula The VDM formula is derived from the net present value formula and can be used to calculate the value of maintenance. The VDM formula is: PVmaintenance = Σ {FSHE,t x (CFAU,t + CFCC,t + CFRA,t + CFSHE,t) / (1+r)t} where: PVmaintenance = present value potential of maintenance FSHE,t = SHE factor in year t CFAU,t = future free cash flow in year t from Asset Utilization CFCC,t = future free cash flow in year t from Cost Control CFRA,t = future free cash flow in year t from Resource Allocation CFSHE,t = future free cash flow in year t from Safety, Health & Environment r = Discount rate SHE stands out prominently in the formula. This factor shows how great the probability is that the License to Operate will be retained in the coming years and that the expected cash flows from all four value drivers will actually be attainable in the future. Consequently, the SHE factor is a probability factor with a value of 0 to 1. A SHE factor of 0 means 0% probability of retention of the License to Operate, for example in a fictitious case where a company decides to stop performing all maintenance for cost reasons. The free cash flow that this creates on Cost Control will be enormous. But because the company fails to satisfy SHE laws and this loses its License