A system for optimizing a travel speed of an off-road vehicle utilizes time-over-target values as a threshold indicator for diagnostics and subsequent remedial actions. A road used for haulage is divided into a plurality of predetermined road segments. A target transit time is defined for each of the predetermined segments to provide a target speed curve. An actual transit time values is measured for the off-road vehicle in transiting the road. A comparison outcome is generated by comparing the target transit time value with the actual transit time value. The comparison outcome is useful in adjusting the travel speed for the vehicle to minimize the time over target value.