It is computationally expensive to find out where vulnerable parts in a network are. In literature a variety of methods were introduced that use relatively simple selection criteria (measured in real-life or calculated in a traffic simulator) to pre-determine the seriousness of the delays caused by the blocking of that link and thereafter perform a more detailed analysis. This paper reviews the selection criteria proposed in the literature and assesses the quality of these criteria. Furthermore, a multi linear fit of the criteria is made to find a better, combined, criterion to rank the links according to their vulnerability. The paper shows that different criteria indicate different links to be vulnerable. Also combined they cannot well predict the vulnerability of a link. Therefore, it is concluded that to find vulnerable links, one has to look further than link-based indicators.