The assessment of the structural safety of existing br idges and viaducts becomes increasingly important in many countries owing to an increase in traffic loads. Most existing standards, however, are developed for the design of new structures. For this reason, an assessment method for determining the actual safety level of highway bridges and viaducts has been developed. The method focuses on the determination of the effect of traffic actions and consists of a number of levels. The first level requires the least work from the engineer but is the most conservative. Each of the next levels is less conservative. Some levels require actual measurements at critical parts of the structure. This paper consists of two parts. The first part explains the basis of the safety assessment me thod and the second part shows the step-by-step application of the method to an existing highway bridge in The Netherlands.