?
Safety assist is a built-in, hand-coded guard. It is not part of Kev.
Ten times a second it predicts the next ~3 s of zombie movement. If the lane Kev is heading for would hit a zombie, it switches to the safest nearby lane, without waiting for Kev's next answer.
Off (default): Kev makes every decision, so the distance shows how well Kev plays. On: longer runs, but the credit is shared. Each override is counted in the stats.