Transportation infrastructure owners manage an array of different asset types such as bridges, road pavements, earthworks and drainage. Currently, most organisation management procedures are siloed by asset type, however there are important interactions between these asset groups that need to be managed in a cross-asset way. Whilst these interactions are known, there is little or no quantification of these interactions. For the first time, this paper quantifies that 74% of Highways England's earthwork failures are a result of drainage related problems, either the lack of drainage infrastructure or the poor performance of it. The analysis undertaken is an important first step in not only moving towards more connected asset management planning for earthworks and drainage, but to also provide guidance for other owners of earthwork infrastructure assets to improve their strategic asset management procedures.