Concurrent causes. Where two separate acts of negligence combine to cause an injury to a third party, each actor is liable. For example, a
construction worker negligently leaves the cover off a
manhole, and a careless
driver negligently clips a
pedestrian, forcing the pedestrian to fall into the open manhole. Both the construction worker and the careless driver are equally liable for the injury to the pedestrian. This example obeys the
but for test. The injury could have been avoided by the elimination of either act of negligence, thus each is a
but for cause of the injury.²