A diverging diamond interchange (DDI), also known as a double crossover diamond interchange, is an unconventional interchange design. The DDI design is able to accommodate heavy left-turn demand more efficiently than conventional diamond interchanges by switching directions of travel for the arterial through movements. The first DDI in the United States opened in 2009, with approximately 37 currently in operation and hundreds more under construction or in the planning phases. This paper presents an empirical analysis of before and after field data collected at two sites under FHWA project DTFH61-10-C-00029, Field Evaluation of Double Crossover Diamond Interchanges. Operational performance data assessed in this paper include traffic volume, saturation flow rate, queue length, delay, and travel time. The study focused on the before and after evaluation of two conventional diamond interchanges at Front Street and I-435 in Kansas City, MO, USA, and at Winton Road and I-590 in Rochester, NY, USA. The field data analysis reveals that DDIs generally operate more efficiently than their conventional diamond interchange counterparts. The Kansas City site had considerable savings in queue lengths and delays for all directional movements, while the Rochester site’s queue lengths and delays indicated somewhat mixed results, showing improvements in a specific directional movement like left turns from the arterial, but exhibiting deterioration in other, less notable movements.