interfaces before reaching the next one. This offers more flexibility in the way the interfaces can be chosen. Here we did so using the edges of cells in a Voronoi tessellation because it is convenient, but the formalism above is clearly independent of that choice and can be applied to any type of interfaces.

Regarding the relation with the Markovian milestoning procedure with Voronoi tessellation [@miles6], the main advantage of the method proposed in this note to compute the rate is that it is exact and hence avoids completely the assumptions underlying milestoning [@miles5]. On the other hand, the new procedure is also more costly since it requires not only to build databanks of re-entry points but also to do the sampling twice – once to get the unbiased statistical steady states quantities, and once more to get the reaction rate by twisting the dynamics. For systems at equilibrium, one may therefore prefer to use the Markovian milestoning procedure with Voronoi tessellation [@miles6] which is cheaper. For nonequilibrium systems, this procedure is inapplicable (since it relies on the time-reversibility of the dynamics), but as a compromise, one could use the nonequilibrium sampling strategy for the unbiased system to compute the 