A System of Systems (SoS) is a class of system composed of a set or arrangement of independent systems that together provide unique functionality for the end user. Due to its complexity, the Requirement Engineering (RE) process needs to undergo adaptations to fit the development of this type of system. In this context, the objective of this work is to propose a approach for the development of SoS, called REAP-SoS. The main characteristic of the REAP-SoS is the derivation of the individual missions and requirements of the constituent systems based on the general SoS assignments. In addition, the approach is also able to derive the requirements of the constituent systems of SoS. To validate the approach, a case study on a SoS urban traffic control and monitoring was performed.