We consider the problem of non-bifurcated multicommodity flows rerouting in survivable connection-oriented networks. We focus on local restoration, in which the backup route is reroutes the flow only around the failed arc. The origin node of the failed arc is responsible for rerouting. We introduce and discuss a new convex function for optimisation of primary routes. We propose a heuristic algorithm for assignment of primary routes employing the developed function. During numerical experiments we examine performance of the new function compared to other functions proposed previously in the literature.