It is illegal to herd livestock down a state highway without proper warning flags.

The Law

You cannot drive a flock of sheep or a herd of cattle along a fast-moving highway without posting flaggers ahead and behind the animals. Idaho is an open-range state in many areas, but driving animals on modern state routes requires strict safety protocols to avoid catastrophic bovine-bumper collisions. Failure to post warnings makes the rancher liable for any vehicular damage.