Various embodiments of the present invention are directed to a fleet management computer system for assessing vehicle efficiency. According to various embodiments, the fleet management computer system is configured for receiving and assessing vehicle telematics data in order to determine an idle percentage of engine run time value representing the percentage of the vehicle's engine run time during which the vehicle's engine was idling during the one or more time periods. In addition, the fleet management computer system may be configured for assessing vehicle telematics data in order to identify segment of engine idle time and generate a graphical display indicating various attributes of the identified idle time segments. The idle time percentage and idle time segments generated by the system can be used to assess the efficiency of vehicles and/or vehicle operators in an associated fleet.