In discussing costs and benefits associated with road safety measures two approaches are possible and are in widespread use. The first approach evaluates all the costs associated with the introduction of a certain safety measure and compares these with the benefits achieved from the reduced number of accidents, casualties or fatalities expressed in monetary values. The second approach does not convert the reductions in accidents and casualties into monetary values, but compares the numbers of accidents saved with the costs involved. This is the cost-effectiveness approach. In cost-benefit calculations different values are adopted for accidents, casualties of varying degrees of severity and for fatalities in different countries. Even the theoretical methods adopted in the different countries are not the same. Some are adopting the gross loss of output approach, some the net loss of output approach and some adopt the approach considered more advanced and correct, the willingness-to-pay approach. This approach is considered by some to be un-ethical and therefore to be avoided. It is however wrong to assume that by taking the cost-effectiveness approach such issues can be avoided. If one safety scheme prevents a certain number of casualties of varying degrees of severity and another scheme prevents a different mix of severities at a different cost, the decision still has to be made how to weigh these different mixes. The monetary conversion adopts one particular mix.