A locomotive monitoring system defines several mutually exclusive operating states for a locomotive. The amount of time the locomotive operates in each state is preferably determined and recorded. This recorded information can then be evaluated with a view towards improving locomotive operations. For example, a plurality of mutually exclusive idle states can be defined and monitored to determine how long a locomotive idles under certain conditions instead of automatically shutting down for the purpose of conserving fuel. In this manner, the sources of lost fuel savings can be readily identified, quantified and addressed. An event log is also provided for chronicling certain operating events of interest over time, such as those relating to the starting, stopping and/or idling of the locomotive's engine.