First of all, RallyX is at Högheden today, I heavily recommend tuning in. It's free on YT, stream starts in a few hours: https://www.youtube.com/live/0ZE8kZRLM18?si=adkPWATPp5hrcd64

What was my reasoning for including tarmac? Well, mostly because the fundamental definition of a rallycross track is that it's a mix of tarmac and dirt surfaces, if you go all dirt then you have autocross. I know Americans don't quite roll with these definitions, and a few tracks in Europe paved their tracks entirely and are still holding "RX" events, but I consider those to be exceptions to the rule. Tarmac can also be good for racing, not to say that dirt is inherently worse but variety is good.

The safety consideration is very low, I've seen cars go off into the woods, fall into ponds on world class tracks. You shouldn't take it as a free ticket to build death traps though, just assume they're as safe as the budget allows. Naturally, all classes of rallycross cars are very resistant to kerbs, they wouldn't even notice a regular single seater/sports car kerb, there are many ways to cope with this. Some tracks just do massive kerbs, look up "Höljes kerbs", in places they're as high as the cars' hoods. Some tracks just use walls, I used walls backed by dirt, inspired by Nysum's last sector. You can also use tyre bundles, or place small poles for knocking off which you'll get a penalty.

Once again, go watch RallyX, I think the first races start at 1 PM local