The mega roundabout is a new type of intersections on the rural multilane highways in the form of an elongated ellipse that combines the best features of the roundabout and unconventional MUT intersection. This intersection was developed in a previous paper using simulation data and found that it is better than interchange (full cloverleaf) in most scenarios of traffic flow. Basically, there are no procedures or guidelines for the mega roundabout design in HCM, FHWA and AASHTO. So the purpose of this paper is to analyse the performance of traffic operations and to propose a methodology for estimating the capacity and level of service of the mega roundabout intersections by gap acceptance theory, to assist practitioners in determining the appropriate geometric design, assessment of mega roundabout intersections and to make comparisons with other alternatives. Explicit VISSIM simulations are conducted to validate the accuracy of the proposed methodology.