  A conic bundle is a contraction $X\to Z$ between normal varieties of relative
dimension $1$ such that $-K_X$ is relatively ample. We prove a conjecture of
Shokurov which predicts that, if $X\to Z$ is a conic bundle such that $X$ has
canonical singularities and $Z$ is $\mathbb{Q}$-Gorenstein, then $Z$ is always
$\frac{1}{2}$-lc, and the multiplicities of the fibers over codimension $1$
points are bounded from above by $2$. Both values $\frac{1}{2}$ and $2$ are
sharp. This is achieved by solving a more general conjecture of Shokurov on
singularities of bases of lc-trivial fibrations of relative dimension $1$ with
canonical singularities.
