Locomotive diesel engine idle time distributions: Case studies from Poland, 2009-2013

Idle times of shunting locomotives were measured in nineteen Polish industrial sidings and analyzed. The current locomotive owner's regulations propose 30 min as the maximum idle time for shunting locomotives. Research shows that the size of a single idle time gap ranges from seconds (most frequent) to 4 h (during winter), but 95% of observed idle times are shorter than 4-11 min (for different types of locomotives). 75% of the idle times cases are less than 1.5 min (47 s if counted only for SM31 locomotive). We fit the distribution of the measured idle times to theoretical distributions, obtaining the best fit for the Pareto type II. If the diesel engine idle time lasts for 9 min then the probability that the given engine will stay in the idle mode for the subsequent 8 min is large, namely, greater than 0.6. These results go along with Weaver (2006). He concludes that if the locomotive idling lasts longer than 8 min then it is more energy efficient to turn off and restart a modern locomotive. Letting it idle for the whole time produces more emissions. If the frequent turning on and off does not reduce the engine life we propose to turn off the locomotive engine after 10 min of unnecessary idling. Automatic Engine Start Stop system (AESS) could (in addition to its main tasks) send reports to the locomotive owner if the engineer deactivates this system too many times.