This may be old news to some, but I imagine it is new news to others (including me). For a long time I just accepted that my track took 3 or 4 minutes to export because it has quite a bit of detail. I've always known that inaccessible things need not have their collision flags set, nor in some cases receive light/shadow. However I never needed to think about turning them off for terrain until just now. I split up my existing terrain segments so that things outside the barriers were separate from the things inside. Then I turned off their collision properties, as well as receive light and shadow (these are from light/shadow cast by objects, not general ambient light). Now it takes just 30 seconds. \o/ It also seems to load quicker in Scene Viewer. I've yet to try it in rFactor, but I expect greatness. Another thing that helps is to deselect the option to overwrite the AIW file. Anyone else have suggestions?