Just wondering how to model "courtesy gaps"; that is gaps that are granted by vehicle operators on a saturated mainline to operators of vehicles on the minor leg of an unsignalized instersection. I have a case where there is a "T-type" unsignalized intersection and there is a heavy volume of turning traffic from the STOP-sign controlled minor leg approach. In reality, vehicles on the mainline actually stop and grant gaps to vehicles turning from the minor leg. Any suggestions on how to model this?

I can tell you a way that didn't work for me, and that was to put yield control on the major street. Left turning traffic onto the minor road would get stuck in the turn pocket and locked up my network. it did passably well for the gaps, but probably too well.
have you tried the channelized right turns? I put one in with stop control with a small radius (maybe 25 feet) and it helped the right turners get into traffic. In my location, I did have traffic queues on the major street back up through this stop controlled intersection, and at that point several left turners we able to turn onto the major street.

Eric