Large-scale collective infrastructure construction is only known in two groups of animals: humans and social insects. Leaf-cutter ants construct networks of cleared trails spanning several kilometres, from which they remove all organic litter and undergrowth. Little research exists on their function or on how they are constructed. I introduce a model calculating costs and benefits of their use, and a simulation of the clearing behaviour based on behavioural experiments. In an evolutionary game theory setting, I explore the connection between trail clearing and territory size dynamics, and how these influenced the evolution of the behaviour.