In my research, we consider the opportunities and challenges of introducing operational flexibility into logistics systems. With more flexibility, it is possible to significantly improve system efficiency (greater utilization of employees and equipment, reduction in empty miles traveled, etc.). At the same time, increasing flexibility expands the set of operational choices (possible vehicle routes, load assignments, etc.) which complicates already difficult routing and scheduling problems. Often analysis of these complex freight transportation systems requires approximations and simplifications in modeling and solution methods to obtain solutions with acceptable computational effort (i.e. computer time and memory).