This lecture is about systems of equations describing the effect of including a line (the "road") with a specific diffusion on biological invasions in a plane (the “field”). In the field, outside of the road, the propagation is of the classical Fisher-KPP type and there are exchange terms between road and field. After introducing the model, I will recall some previous results about the effect of the road on the asymptotic speed and shape of invasion in terms of the parameters. I will also report on recent works on two new variants of this system. First, I will describe the effect of a strip rather than that of a line (and analogously, say, of a tube in dimension 3). Then, I will discuss the influence of the road in the context of an ecological niche and what happens when there is a climate shift.