Ok right now cautions just annoy people because they happen late in the race all the time, and only a few inactive people cause them.
This needs to be changed.
-Make sure it can happen any time in the race (the inactive people can still cause them, but they will likely break down any time during the race. Also speed up the inactive people a little.)
-Anybody else has a small chance (maybe like 5 percent per full race for a level 10), to spin or crash. You can train your drivers, like other abilities, to avoid wrecking.
-A caution would last about 2-4 laps, and people would bunch up behind a pace car. The lap cars would line up at the back.