NextGen and SESAR are re-defining each agent's role in the airspace in terms of autonomy, authority and responsibility. Function allocation is the process of defining authority, i.e., which functions are executed by which agents. This is an essential design decision in creating transformative ATM concepts of operation. This paper presents a computational simulation methodology to assess function allocations in early design phases, before functional prototypes and HITL experiments can be developed. Thus, this method applies the same models of the functions regardless of which agent executes them, so that any observed effects can be isolated to the function allocation without confounds. A case study is presented in which ten potential function allocations within a new concept of operation were evaluated. A distinction is made between coherent and incoherent function allocations. The key metrics of the function allocations include the time history of each agent's task load and required information exchange with other agents. The results show that the coherency of a function allocation can have a pronounced effect on the amount of information requirements. The paper concludes with a discussion of how this method can be applied to other concepts of operation, and how this method can be used, after the early-in-design analysis described here, as an evolving computational analysis tool for more detailed evaluations using higher fidelity models.