We as software engineers are responsible for the long-term consequences of the systems we design - including impacts on the wider environmental and societal sustainability. However, field lacks analytical tools for understanding these potential impacts while designing a system, nor for identifying opportunities for how to use software to bring about broader societal transformations. In this article we explore how the concept of leverage points can be used to make sustainability issues more tangible in systems design. Using the example of software for transportation systems, we illustrate how leverage points can help software engineers map out and investigate the wider system in which the software resides, such that we can use software as an effective tool for engineering a more sustainable world.