When modeling a roadway with a large median, it can sometimes be difficult to determine if it should be modeled as one intersection with median or as two separate intersections. Ask yourself this question: 'Do drivers ever stop in the median?' If they do, then it should be modeled as two separate intersections. Let's look at a real life example...
Here you can see two nearby intersections that are geometrically similar, but drivers are treating the median differently.
On the northern intersection, there are vehicles stopped in the median waiting to turn. You may also notice there are stop lines in the median, encouraging this behavior.
In contrast, drivers travel through the southern intersection with a single maneuver. There are no stop lines, and no vehicles stopped in the median.
In order to model this behavior in SimTraffic, the southern intersection should be modeled as one intersection with a median. The northern intersection should be modeled as two separate intersections, that may operate on a single controller using the Cluster Editor.
Here are the same intersections coded in Synchro. Each node is numbered. With this type of setup, vehicles in SimTraffic will treat both types of medians correctly.