  We prove that any polynomial-time $\alpha(n)$-approximation algorithm for the
$n$-vertex metric asymmetric Traveling Salesperson Problem yields a
polynomial-time $O(\alpha(C))$-approximation algorithm for the mixed and windy
Capacitated Arc Routing Problem, where $C$ is the number of weakly connected
components in the subgraph induced by the positive-demand arcs---a small number
in many applications. In conjunction with known results, we obtain
constant-factor approximations for $C\in O(\log n)$ and $O(\log C/\log\log
C)$-approximations in general. Experiments show that our algorithm, together
with several heuristic enhancements, outperforms many previous polynomial-time
heuristics. Finally, since the solution quality achievable in polynomial time
appears to mainly depend on $C$ and since $C=1$ in almost all benchmark
instances, we propose the Ob benchmark set, simulating cities that are divided
into several components by a river.
