Abstract We study map lattices coupled by collision and show how perturbations of transfer operators associated with the spatially periodic approximation of the model can be used to extract information about collisions per lattice unit. More precisely, we study a map on a finite box of L sites with periodic boundary conditions, coupled by collision. We derive, via a non-trivial first-order approximation for the leading eigenvalue of the rare event transfer operator, a formula for the first collision rate and a corresponding first hitting time law . For the former we show that the formula scales at the order of $$L\cdot \varepsilon ^2$$ L · ε 2 , where $$\varepsilon $$ ε is the coupling strength, and for the latter, by tracking the L dependency in our arguments, we show that the error in the law is of order $$O\left( C(L)\frac{L\varepsilon ^2}{\zeta (L)}\cdot \left| \ln \frac{L\varepsilon ^2}{\zeta (L)}\right| \right) $$ O C ( L ) L ε 2 ζ ( L ) · ln L ε 2 ζ ( L ) , where $$\zeta (L)$$ ζ ( L ) is given in terms of the spectral gap of the rare event transfer operator, and C ( L ) has an explicit expression. Finally, we derive an explicit formula for the first collision rate per lattice unit .