Usually, dynamic routing metrics consider the instantaneous load and the static structure of a network to determine an optimal path. This paper proposes an extension of the path selection process that is imposed by advance reservations. In the scope of scheduling Grid workflows advance reservations are likely to become a cornerstone which introduces temporal aspects. The focus of this paper is to extend the concept of dynamic routing with the notion of time. This paper classifies and proposes specific temporal routing metrics and presents ways to integrate these metrics into routing algorithms.