Abstract
We define a transverse correlation length suitable to discuss the finite-size scaling behaviour of an out-of-equilibrium lattice gas, whose correlation functions decay algebraically with the distance. By numerical simulations we verify that this definition has a good infinite-volume limit independent of the lattice geometry. We study the transverse fluctuations as they can select the correct field-theoretical description. By means of a careful finite-size scaling analysis, without tunable parameters, we show that they are Gaussian, in agreement with the predictions of the field theory proposed by Janssen, Schmittmann, Leung and Cardy.