In the same study (8), Gartner also proposed a rolling horizon approach to predict
traffic arrivals such that the constraint of knowing exact traffic arrivals was removed. By
adding the rolling horizon prediction method, OPAC-2 evolved into OPAC-3 (41).
Gartner evaluated the OPAC-3 control strategy using a special version of NETSIM. The
evaluation was based on data collected from an intersection in Tucson, Arizona. The
results showed that compared to the existing control method deployed at that intersection,
OPAC reduced average delay by 30-50 percent and increased average speed by 10-20
percent. Although the improvement from OPAC was significant in this study, Gartner
did not specify if the original control strategy was optimized or not.