In O'Donnell v. City of Casper, 696 P.2d 1278 (Wyo. 1985), the Court discussed the viability of the exception in light of the adoption of comparative negligence. Mr. O'Donnell operated a motorcycle and encountered an accumulation of gravel remaining on the street from a resurfacing project performed by the City of Casper. The Court distinguished the facts in O'Donnell, an instance of injuries arising from a man-made cause, where the city placed gravel on the street and allowed it to accumulate in ridges and piles, from instances in which liability arises from natural causes.