We develop a simple linear time algorithm to determine if a collection of two-pin  nets can be routed, topologically, in a plane (i.e. single layer). Experiments indicate  that this algorithm is faster than the linear time algorithm of Marek-Sadowska and  Tarng [1]. Topological routability testing of a collection of multi-pin nets is shown to  be equivalent to planarity testing and a simple linear time algorithm is developed for  the case when the collection of modules remains connected following the deletion of all  nets with more than two pins