We have studied the methods to operate single electron circuits with high reliability at room temperature. By simulation, we have numerically analyzed the error mechanisms of the room-temperature operation of a 2-gate electron pump as a fundamental single electron element circuit. We have found from the results that under the room temperature condition where the ratio of the electrostatic energy to the thermal energy for a transition electron is not so large, the minimum operation error probability is obtained at the specific gate sweep time when the circuit is operated with ramp-waveform control voltages. The analyses indicate that in the shorter sweep time range, the error probability increases because the gate voltage has changed before the significant electron transition occurs, and that in the longer sweep time range, the error probability also increases due to undesired-single-transition events. The optimum sweep time is estimated statically with the relationship between desired- and undesired-single-transition rates as a function of control gate voltages. Using the optimum condition, the operation reliability is expected to be improved by a factor of 100. This estimation method has been also confirmed by the time-dependent Monte-Carlo simulation.