I once showed the ep.6 of Initial D Fourth Stage to a friend, who is a semi-professional racer. I knew already that the depiction of hashirya culture was realistic. But this time we were considering the racing element. I chose that specific episode because it contained a whole battle (most battles take 2 or 3 episodes). So, the verdict?

The "disappearing line", which Tomoyuki applied to Takumi with such effect, turned out be real. Only in American racing it is called "slobbing". And what's funny, by the 2nd half my friend was shouting, "Bump him! What are you waiting for, bump him!" Oh, my cookies. Initial D mangaka and writers knew their stuff.