Contemporary transport infrastructure planning is typically built upon the core belief that physical mobility has inherent advantages and that more of it will always yield better socio-economic outcomes. Such an embrace of maximum growth yields a misguided calculus for planning transport infrastructure. Rather than seeking to meet the demand for future mobility by reflexively expanding the quantity of infrastructure, there is a need to consider alternatives that can support a sustainable future. By applying the ‘half-life’ concept to transport infrastructure, this paper explores alternatives to extending its use in perpetuity that open up a wide range of possibilities.