Transportation planners require software support to easily monitor and dispatch transportation resources, especially when transportation is multi-modal and when resources from different companies in their network are being used. We call such an application a transportation control tower. This paper presents a software architecture for transportation control towers. It focuses in particular on the novel aspects of the software architecture. These are: the ability to easily configure the monitoring of resources and tasks; the ability to create the statements for monitoring resources and tasks based on the transportation plan; and the ability to dynamically adjust the monitoring statements. A prototype of the software architecture is implemented and evaluated on three usage scenarios.