How to change amount of random encounters and critter types, which attacks caravan, when travelling with caravan?
Best answer for you - look into script .SSL of caravan manager(s) who sends you to caravan run via dialog (you can identify script name by searching some known text in data\text\english\dialog folder).
Actually I think all that is defined in the huge BHRNDST.H. I tried the caravan masters too, but they don't really make it run I think.