  We present a randomized distributed algorithm that in radio networks with
collision detection broadcasts a single message in $O(D+\log^2 n)$ time slots,
with high probability. In view of the lower-bound $\Omega(D+\log^2 n)$, our
algorithm is optimal in the considered model answering the decades-old question
of Alon, Bar-Noy, Linial and Peleg [JCSS 1991].
