Railroad grade crossings are rare on freeways. But on the US 63 bypass on the northeast side of Columbia, built in the mid-1990s, there's a crossing with the Columbia Terminal Railroad (COLT). There have been several fatal accidents at this crossing. Most resulted when a speeding vehicle rammed into the back of a school bus stopped at the grade crossing. By state law, school buses must stop at all railroad crossings. In response to public concern, large yellow warning signs were erected. Even so, there have since been at least two fatal accidents at the COLT-US 63 crossing.