with our simulation result for the mean time τ for a particle to hop between adjacent wells when there are no other particles in the system. Thus the mean-field curve in Fig. 10 agrees with simulation in the low-density limit. To estimate the transition rate j (1 , 1 , 0), we perform a Monte Carlo simulation to determine the mean time required for a particle to hop to the next well, when the preceding well is occupied, and there are no other particles in the system. This yields 1 /j (1 , 1 , 0) = 5 . 548 s. Although the presence of the trailing particle leads to an increase of about 18% in j , the effect is not sufficient to yield quantitative agreement with the current observed at higher densities (Fig. 10). There are two possible sources for this discrepancy. First, at moderate and high densities, strings of n ≥ 3 occupied wells occur with finite probability, and the cumulative effect of repulsions along the chain should make the hopping rate of the lead particle an increasing function of n . Simulations of n = 3 - 9 occupied wells show that the transition rate of the first particle grows with n , but not enough to account for the maximum value of the current observed. A second point is that the mean-field factorizations P (0 , 1 , 0) = ρ (1 − ρ ) 2 and P (1 , 1 , 0) = ρ $^{2}$(1 − ρ ), are not very accurate in the continuous-space model. For density ρ ≃ 0 . 52, for example, we find and implying a significant correction to the mean-field theory predictions. P (0 , 1 , 0) ρ (1 − ρ ) 2 ≃ 1 . 21 (20) P (0 , 1 , 1) ρ $^{2}$(1 − ρ ) ≃ 1 . 04 (21) 21