In Crowell v. City of Philadelphia, 531 Pa. 400, 613 A.2d 1178 (1992), the driver of a vehicle caused a fatal accident after he followed a directional sign placed by the City and drove the wrong way down a one-way street. The Political Subdivision Tort Claims Act specifically waives immunity for "a dangerous condition of trees, traffic signs, lights or other traffic controls ... under the care, custody or control of the local agency...." 42 Pa. C.S. 8542(b)(4). In any case, a misplaced directional sign renders a street unsafe for its intended purpose. The parents of a three-year old boy killed in a head-on collision sued the City of Philadelphia after a vehicle followed an incorrectly painted arrow which directed it into oncoming traffic. The City asserted the defense of sovereign immunity. The jury found unequivocally that the action of the City's employee in misplacing the directional sign was a substantial contributing cause of the accident. The Supreme Court upheld the verdict because the City's action did not merely facilitate the injuries but was in fact a substantial contributing cause of them. Even though the directional sign itself did not strike the child, its position did cause another vehicle to travel the wrong direction into the path of plaintiffs' car and cause the child's fatal injuries.